Counterstrike's premise was that there was a group of aliens (from Alpha Cantauri - aren't they all?) planning to take over the Earth, and another group (the 'observers') dedicated to stopping them. At all costs the humans are not to know that this clandestine battle is going on.

Unfortunately, when the primary Observer ends up in hospital, his secret is divined by his doctor - who joins him in his assignments.

Simple premise, but it had the advantage that it needed a minimum of SFX and relied totally on plots and acting.

The unbroadcast/wiped episode wasn't lost because of a strike though - the BBC pulled it in favour of a documentary on the Kray twins, who were sentenced on the day that episode was due to go out.