Eager to move away from producing the puppet series with which they had made their names, UFO was Gerry and Sylvia Anderson's first attempt at a totally live action sci-fi TV series.

Set in the 1980s, the series saw the Earth being visited by aliens whose intentions were certainly not friendly. Defending us from this alien menace was the secretive SHADO (Supreme Headquarters Alien Defence Organization), under the control of Commander Ed Straker. Being a military organisation SHADO was well equipped to deal with the menace — the orbiting SID (Space Intruder Detector) was on permanent watch for any incursions into Earth's solar system, and any ships detected would immediately find themselves under scrutiny from the Interceptors which could be launched from SHADO's base on the moon at a moments notice.

After a first season of twenty-six episodes it was thought that the series would return for a second year, but plans for another season were hastily shelved after the ratings for the series went into decline in the United States.

Rather sadly, the proposed UFO: 1999 soon found itself mutating into the rather more unwelcome form of Space: 1999...

All twenty-six episodes of the series have been released on DVD.