For historical value, this is great. It's the first time UNIT is mentioned, and the company involved in bringing the cybermen to Earth is mentioned in the 10th Doctor episode Rise of the Cybermen. But the story goes nowhere, the Doctor is completely useless, and it's just not a Doctor Who story. It's a military story, a shoot-em-up. The characters make pointless, destructive choices, at one point getting soldiers killed, and there are no consequences or second-thoughts. And it dragged on for 3 1/2 hours. The show's come a long way since this one.