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I Spy: My Life in MI5

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'One of the most successful MI5 undercover surveillance officers of his time' Sun

Tom Marcus spent years of his life undercover, waging a secret war on the streets against those who want to do us harm. Now, for the first time, he tells the full story of what it is like to live your life in the shadows and who you need to become to survive.

First published in 2016, Soldier Spy was a series of stories from Tom's years in MI5 and has now sold over 250,000 copies across all editions and was a Sunday Times bestseller for five months. I Spy takes us even deeper into the ongoing battle to keep us all safe.

260 pages, Kindle Edition

Published May 30, 2019

168 people are currently reading
1070 people want to read

About the author

Tom Marcus

14 books163 followers
Tom Marcus, former MI5, grew up on the streets in the North of England. He joined the Army at sixteen and went on to became the youngest member of the Armed Forces to pass the 6-month selection process for Special Operations in Northern Ireland.

He was hand picked from the Army into MI5 as a Surveillance Officer. He left the Security Service recently after a decade on the frontline protecting his country due to being diagnosed with PTSD.

An extraordinary battle and recovery took place which led Tom to write his first book, Soldier Spy which has been vetted and cleared for publication by MI5, it's the first true ground level account ever to be told. The first time in the Security Services' history a Surveillance Officer has told the real story of the fight on our streets and his debut book went straight to Number 1 on the Sunday Times best sellers list and Number 1 on Amazon.

Tom's new fiction series featuring Matt Logan starts in May 2018 with his first book; Capture or Kill.

Tom, now consults on projects within TV and film including the TV dramatisation of his book Soldier Spy.

Due to the ongoing specific threat to Tom Marcus, MI5 insist he keep his identity hidden and he continues to work with the Security Service and other agencies to ensure he stays safe.

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5 stars
723 (37%)
4 stars
680 (34%)
3 stars
405 (20%)
2 stars
104 (5%)
1 star
38 (1%)
Displaying 1 - 30 of 138 reviews
Profile Image for Leo.
4,984 reviews627 followers
April 21, 2021
A nonfiction about Tom Marcus life as a spy for MI5. It was indeed very interesting, having only read a handfull of spy novels, I wanted to know how the real life was as a spy and not only the fiction and Hollywood movies side of things as they tend not to mirror the reality that well. It's a good book and I enjoyed the audio but spies and such is maybe not my favorite subject so I didn't get that much out of it. But I'm glad I've read it and it's a good base of knowledge when I'm reading fiction of spies.
Profile Image for Simon.
192 reviews9 followers
May 31, 2019
Mesmerising!

From the opening scene to the end this simply had me in thrall. I'll claim no expertise on how authentic this actually is, after all my knowledge of MI5 is made up of the output of various thriller writers and not much more. However, it feels real, the authenticity promised by an ex-operative seems to be delivered in spades.

A big part of the reason for this, it has to be said, is the excellent narration by Jason Langley, he strikes just the right tone and in combination with Marcus's writing it felt possible to imagine being out there as part of a surveillance team, alone in a bar of strangers or flat out in the grass of a Welsh hillside.

Just how complete a picture it is we can't tell, after all I am sure that MI5 would take a dim view on too much of their operational procedure being revealed. It is though fascinating and what's more it also provides examples of the toll that this dangerous, highly pressurised work has on those who do it. And thankful we are that they do!

If you liked the previous books by this author and want some more then this delivers brilliantly.

Profile Image for RG.
3,084 reviews
June 22, 2019
Was kind of expecting a pulse pounding novel. Would have loved more action in a way. The best part was his childhood.
131 reviews4 followers
January 12, 2023
A thoughtful Christmas gift from my eldest. It was a very entertaining book, quite insightful into MI5 surveillance and the author’s own struggles with PTSD. You have to admire his craft as a spy and his ability to let you into that life without over dramatising it. However I found it a bit repetitive. He does tell quite a few operational stories but the action becomes a bit skippable. That said it’s been a while since I romped through a book having failed last years reading challenge by a country mile so a good start to the reading year. One down, 22 to go…
17 reviews
July 18, 2020
Pretty disappointing, padded out with 2 stakeouts using code names in Capitals (BD to ZVictor 1 etc.) constantly to fill the page, both stories could have been told in a few pages.
Gratuitous invective ( mostly when not required).
Gave the impression that the author was trying to fill a story to make a book and look for sympathy. Using family to explain why mind not on the job!
Presumably all the names are false and all the stories fictitious but didn’t achieve any believable situations. Not worth the bother, bottom of the list
Profile Image for Logan Horsford.
577 reviews21 followers
June 1, 2019
Pretty good book.

Yeah, it's a tough life to leave behind and you never really do.

I've not yet read the other book by Marcus but will do so.

After exercising some of the demons writing about himself, a possible next step would be to do fiction. He made the lamplighters/pavement artists/surveillance people interesting and suspenseful.

I'd like to see that brought into a fictional (no gag notices to worry about!) arena next. It's an interesting peep into an entirely different lifestyle. With a very human protagonist.

Cheers!
Profile Image for Rob Thompson.
745 reviews43 followers
July 5, 2019
Fiction or non-fiction?
Thought it would give a reasonable insight to MI5 and the job but I was rather underwhelmed. Its not an exciting, seat-of-your-pants memoir filled with suspense. Yes, he shares personal stories; Tom is obviously a decent bloke. Yes, I'm glad there are people like this keeping us safe on our streets. And yes, I'm glad her found happiness in writing.

But I was a bit ... bored.

Did not finish.
Profile Image for Nick Davies.
1,739 reviews59 followers
February 8, 2025
This was different to what I expected - I think I'd not read the blurb in detail so was anticipating something a little more office-based analyst/intelligence. What we have here is an honest and open memoir of an ex-operative for MI5 who here discusses a number of surveillance operations (mostly anti-terrorism) he was involved in. The final chapters discuss his having to leave the service due to PTSD and make for some eye-opening and frank reading.

Alas though I'm glad I did read it, I found the majority of the book a little impenetrable. Partly the need to not include a lot of detail about aspects of his job that are best kept secret. Mainly however due to the fact much of the book consisted of page after page of dialogue along the lines of "Alpha six, confirm RED PIGEON is zero three zero oncoming" "Roger, PURPLE SPANIEL in contact, check" "Check three. Charlie four - GREEN OCELOT and WHITE COCKWOMBLE approaching, withdraw all units", and I just couldn't follow so lost interest. It's good that people are doing this sort of thing to keep us safe, it's not necessarily insightful past a point to read about it.
908 reviews
June 17, 2019
I've always been a fan of spy stories, with John Le Carre probably my favourite story teller of the genre. "I Spy: My Life in MI 5" takes us into the real world of spying from the perspective of Tom Marcus whose life inside MI 5 gives him a unique perspective of that murky world.

Although his stories are edgy and fraught with danger and terrorism activities. Of course the old enemy Russia is still the new enemy and the MI 5 operatives are totally focused on preventing daring plots . They have to rely on their quick wits, their resolute training and of course their courage.

In fact Tom Marcus gives John Le Carre a run for his money, and that's high praise indeed.
Profile Image for Michael Rumney.
778 reviews6 followers
January 9, 2021
Tom Marcus tells us about his early childhood and some of the operations he was involved with in MI5.
There is a certain tension as he relates the operations as he and his team deal with terrorists, but there is always a threat from Russia.
This is an easy read which is to the point, something to be expected from someone who is ex military.
In his narrative Marcus is very observational, perhaps too much and there is an overwhelming sense of paranoia.
He wants a family life but he cannot settle.
Apart from being an author you do wonder after reading this, what is he doing now?
Profile Image for Jeita Hartwell.
46 reviews
October 7, 2025
These stories sound like a teenager dreamt them up after a late night of COD. None were suspenseful, nor were the stakes high enough, nor is there any way to know if they’re true or not. The incessant radio communication transcripts (which mean nothing to the average reader), the CAPS LOCK CODE NAMES OF FACELESS VILLAINS and the size 16 font all suggest a book that was contractually obliged and wholly unnecessary.
434 reviews5 followers
October 21, 2019
The book is random pick on my reading.. Just because of wanting to complete the target of Goodreads.

The book is a very detailed communication between the spies.. It has no proper story but is a good read to understand PTSD in professional security providers.

It feels half story.. I think next book will come soon.
This entire review has been hidden because of spoilers.
314 reviews1 follower
August 17, 2020
Book club group read so no spoilers.

To be honest couldn’t give this anything other than 5*. Will be reading Tom’s other books.
All I can say fascinating read and thank goodness there are people out there like you Tom doing such an amazing job and getting no recognition for it either. Just so insightful and we wouldn’t be as safe as we are without you all. Thank you to you all.
Profile Image for Tom Ashton.
Author 4 books10 followers
May 6, 2025
An interesting piece of non-fiction depicting true life in the British secret service.
Turns out reality being an agent is a far cry from Aston Martins and Martinis, and more about scrabbling around in dirty lofts and dealing with PTSD.
8 reviews
August 11, 2025
A gripping read for fans of emergency services and espionage, offering a real-world look at the incredible work they do.
Profile Image for Angela Moore Garden Tea Cakes and Me.
199 reviews25 followers
January 11, 2021
A fast paced and insightful book about the surveillance teams at MI5 working for the safety of our country. I listened to this as an audiobook, the narrator added real drive to this great read. Felt very immersed into the story.
Profile Image for Redmakesmyheartsing.
376 reviews
September 7, 2022
This is the true story of Tom Marcus's life in MI5, but it reads like a James Bond novel. From the first page, I was fascinated by the detail that Tom used to describe the various missions he was involved in. He gives no secrets away but still manages to make you feel you are beside him in the heat of the action. The writing flows very naturally. It felt possible to imagine being part of the surveillance team, whether hidden in grassland on a Welsh hillside or alone in a pub full of strangers.

This book is a page-turner. It is a fascinating glimpse into the highly pressured work that the MI5 operatives do. The teamwork of these highly trained people is beyond amazing they are like a well-oiled machine watching out for each other whilst doing this hazardous work.

On the flip side, Tom's private life is interwoven into this story. He has a young son and a beautiful wife, and he starts becoming obsessed with keeping them safe. His job nearly destroys him by its all-encompassing nature and unsocial hours. Tom starts to think that every shadow is out to get him and is finally diagnosed with PTSD, but with the help of his ever-supportive wife, he starts to live a life in the real world and begins to work on his demons.

This is a highly readable book. I would recommend it to anyone who is interested in learning a little about the workings of MI5, and I think anyone who enjoys spy novels would enjoy this book too.
255 reviews
August 22, 2022
I enjoyed the book but felt a lot of the stakeouts and following suspects was repetitive. Do they really give them such daft code names?!
I thought the ending seemed abit rushed. You’re in the thick of the action then you’re not. An enjoyable read though.
159 reviews9 followers
June 17, 2019
I was rather underwhelmed by this book. I was hoping for an exciting, seat-of-your-pants memoir filled with intrigue, but I was mostly bored. The most interesting part of the book for me was when he talked about his childhood and how that affected who he was and what he became. I'm still looking for a must-read book revolving around true-to-life spy craft. This did not hit that mark for me.
69 reviews1 follower
August 20, 2019
Real life stories from an ex MI5 agent, these are gripping. They're all true which gives it the scare element. An insight into the real world we live in.
Profile Image for Emily Taylor.
223 reviews
July 20, 2021
I really enjoyed this book. Something different, real and exciting.
Profile Image for Mark Sohn.
Author 6 books17 followers
October 24, 2019
Frightening. The comfortable life we lead in Britain is an illusion. I knew this from my own experiences, but those of 'Tom Marcus' (A pseudonym, obviously) are horrifying. This man went from undercover work with the British Army in Northern Ireland to the M.I.5.* 'Watcher' teams; unusually, he was recruited, as most members of these elite surveillance teams are volunteers. He spent years on our streets in various guises right under the noses of the worst terrorists on the Planet - those that would do harm to helpless civilians, even children returning from a school trip. These people showed no compunction or remorse about their actions and neither did Marcus and his colleagues, unsung heroes who worked long hours in appalling danger to keep the rest of us safe. I enjoy life a little more knowing people like this are there to protect us, but Marcus himself paid an awful price. His young family saw almost nothing of him as the workload and PTSD were taking their tolls and, finally, he was forced to leave the job he lived for. An incredible book filled with details, although some are changed for operational reasons - you cannot fail, but to turn the pages on this one as he takes you on spying missions in the most mundane places imaginable. Forget Bond - this is the real thing. I recommend you read 'Soldier, Spy' by the same Author first, though it's not essential - but both books are rare insights into a closed world. 10/10. *Yes, it's the Security Service, but everyone still refers to it by the old name.
19 reviews
October 22, 2020
This book marks the second title that I've read from Tom Marcus, and I was not disappointed. The fast-paced action never lets up. Pulls you in like a portal to a fascinating world of British spies and foreign spies at secret war with each other. Tom Marcus isn't another person in this book—you "become" Tom Marcus in this book as you feel no separation between yourself and the main person of the story.

Like with the previous title, I do have one complaint about the book. It started to grate on me the longer I read it because you could sense the ego from this guy. I'm talking about the parts where he was like, "I'm the best at this job," and "I keep people safe...you flip fries for a living," was basically the gist of it, but I felt like the ego was overtaking the story at points with statements like this. I didn't feel like it contributed to the story and bogged down the overall writing.

Outside of that, Tom Marcus told a gripping story that reveals the interesting world of spies and the work done in counterintelligence operations. This book and his previous book got me to thinking about how spy work gets done. I never used to think about how a spy might be that maniac racing recklessly down the highway. I'm grateful for this book because it contributes more to my perspective.
311 reviews
January 12, 2020
Knygos pavadinimas aiškiai apgaulingas. Skaitytojas vargu, ar ras paslapčių ar kitų momentų, tiesiogiai susijusių su žvalgyba. Autorius daugiausia skiria dėmesio paprastiems taktiniams dalykams. Net ir apie juos rašydamas jis vis vien sugeba nedaug ką pasakyti. Tačiau nesitikėkite perskaitę sužinoti 21 amžiaus žvalgybos ar valstybių paslapčių. Antra vertus, skaitytojas neliks abejingas autoriaus gyvenimo istorijai. Tai negali nejaudinti.
The title of the book is definitely deceiving. The reader will hardly find secrets or other aspects of intelligence activities described here. The author focuses on very tactical and simple things. Even writing about them he manages not to disclose almost anything. Don't expect to learn about the 21st century intelligence or state secrets. on the other hand, the reader will not stay impartial to author's life story. It is certainly extremely exciting.
16 reviews1 follower
June 24, 2019
Very much enjoyed this book, like I did Soldier,spy. This book has a more relaxed feel to it than Soldier,Spy and a lot less anti Police . Maybe this is due to his seemingly better mental health position than in Soldier,Spy? I found it quite interesting to try and decipher where events had to be changed to protect security and the identity of the author ( for instance how his father died/the funeral and his post MI5 job interviews must have been changed as it would be easy for anyone there to piece the puzzle together ).
Whatever details have been changed is not that important to me , what is important is that we recognise what the author did and remember and respect that there are people like him who put life and limb on the line everyday ( without us realising) and give thanks for that . I do hope he releases more non-fiction in the future .
This entire review has been hidden because of spoilers.
Profile Image for Pedro.
54 reviews5 followers
January 12, 2020
Favourite passages:

Your life is filled with defining moments, some good, some horrific. Experiences that shape you for the better and memories that feed the worst parts of your future actions.

It’s only looking back on it now that I realise how, even at that young age, people have the ability to compartmentalise horrific situations so they can survive. I never thought about that evening again. Being able to lock memories and feelings away like this isn’t a fail safe, though, it’s a ticking bomb.

The more you expose yourself to risk, the more resilient and stronger you become. You know you can’t rely on anyone else and you don’t need to.

Everyone is hiding something, even if it’s only from themselves.

Good mental health takes the same care as physical health - you have to take daily preventive measures to make sure you stay fit.
This entire review has been hidden because of spoilers.
Profile Image for Pipa.
298 reviews3 followers
July 29, 2020
This was really interesting. It was very well written and fast paced, giving us just enough about his work and his family to make the book quite well-rounded. However although this is a memoir it’s difficult to trust somehow; a man who has been taught to be so private and hyper-vigilant surely wouldn’t write a book that is an amazingly accurate depiction of his work and life? Places and names must have been changed - but I get the feeling that it’s all a little bit true, and also quite untrue as well. Who knows.

If you’re not overly bothered about it being a genuine memoir, it’s a good book. I think it does lend some good insights and I was hooked the whole way through. The author has clearly overcome some tremendous adversities and been through some terrible traumas. He clearly loves his family very much which is also enormously heartwarming.
Profile Image for Luc.
44 reviews
August 2, 2019
Great insights on life as an MI5.
Loved the wife's perspective on authors mental state late in the book but found the book a bit long and repetitive.
Seemed part of the job but I yearned for some resolution to the stakeout events laid out. Must make for a frustrating job, agents having to rely on platitudes such as "kept the world safe" instead of being debriefed on how events unfolded.
I was also left with the feeling that MI5 chews up and spits out its agents, not providing help to find jobs for their ex-agents once they served. It's one thing for agents not to be able to talk about their work with MI5, but not being able to leverage that expertise to help find employment afterwards is nasty.
This entire review has been hidden because of spoilers.
1 review
November 3, 2019
Wow. What a read!

I love learning about espionage and greatly appreciate the “boring” sides of this story because they’re so authentic and tense. Tom Marcus is a humbling and honorable soldier and his story speaks volumes of his character as a human being. This is the first story I’ve read but I’m glad I did. As a US citizen, my experience with military personnel is often the raging hard-on, hyper macho type, so reading this and hearing how humble the author is made me feel proud for his service.

I’m really glad that Tom became a writer and shared his talent for writing because his style is engrossing, again, even during the “boring” parts.

Next up is Soldier Spy and then onto his novels.

Good read!!
Displaying 1 - 30 of 138 reviews

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