Do you ever think about the opportunities you turned down? I’m not really one for regrets but I definitely ponder those Sliding Doors moments more as I get older.

About 5 years back, I was offered the opportunity to write a Doctor Who story featuring Bernice Summerfield. I’m a massive, massive fan, so this should have been a no-brainer. 

I said no.

I think about this a lot. A LOT. What was wrong with me? Why did I say no?

Firstly – and honestly – there was definitely a fear factor. W...