It all looks a bit rough and ready sometimes, but it is performed with resounding theatrical panache.

A number of decent performances and a gritty realistic view of London makes this little sci-fi spin-off still worth a look.

It was the enormous success of this Hammer version of Nigel Kneale's TV series which began the whole horror boom in Britain.

The lead characters are a little stodgy and Donlevy is about as far away from the modern idea of a film hero as it’s possible to get, but this is still a gritty, surprisingly creepy and graphic story.