Nigel Kneale created sci-fi on British TV. His 1950s Quatermass serials created the three main sci-fi plots still in use today:

• "We go to them" was the 1953 Quatermass Experiment, where an Astronaut returns from space and turns into an alien.
  
• "They go to us" was 1955's Quatermass II, in which zombie aliens invade.
  
• "They've always been here" was 1957's immortal Quatermass & The Pit.
  

In each serial, plucky Professor Bernard Quatermass of the British Rocket Group would overcome alien invaders in between some serious science and drinks at his club. He was TV's first hero - and everyone, from Doctor Who through to Fox Mulder owes him a huge debt.

Quatermass II was the second, and most horrific of the serials. It was transmitted live in 1955, with later episodes preceded with a unique warning for those of a nervous disposition.

The plot tells of an alien conspiracy that is taking over the British government, turning ordinary people into zombies, stopping at nothing to build their own breeding tank in a mysterious chemical factory.

There's a lot to marvel at:

• the fact that it was (just) possible to tell such a complex story live, with only a few minutes of filmed location work inserted each week
• that nothing goes badly wrong
• that there are special effects (for the previous adventure, the author ended up playing the monster using a rubber glove covered with moss).