UFO is a 1970 British science fiction television series about the covert efforts of an international defence organisation (under the auspices of the United Nations) to prevent an alien invasion of Earth.

A single series of 26 episodes (including the pilot) was filmed over the course of more than a year; a five-month production break was caused by the closure of MGM-British Studios in Borehamwood, where the show was initially made.

Early warnings of alien attack came from SID, the Space Intruder Detector, an unmanned computerised tracking satellite that constantly scans for UFO incursions.

[6] The second line of defence includes Skydiver, a submarine mated with the submersible, undersea-launched Sky One interceptor aircraft, which attacks UFOs in Earth's atmosphere.

[8] On Earth, SHADO also uses two SHADAIR aircraft, a Seagull X-ray supersonic jet (e.g. in the episode "Identified") and a transport plane (e.g. in "A Question of Priorities"); a transatlantic Lunar Carrier with a separating Lunar Module (e.g. in "Computer Affair"); a helicopter (actually, a small VTOL aeroplane with large rotating propellers, e.g. in the episode "Ordeal"); and a radio-controlled Space Dumper (e.g. in "The Long Sleep").

Producer Gerry Anderson later said that he had lost his temper with her so badly on the set of UFO that he always feared the idea of running into Michael Caine at some actors' function, and being punched on the nose by him.

The list below, drawn from Chris Bentley's The Complete Book of Gerry Anderson's UFO,[11] details the running order shown on ATV (in the Midlands).

The North American DVD release of the series usually follows the production order, with a few diversions; a website ufoseries.com for the show offers seven possibilities of viewing sequence.

Anderson worked with his wife, Sylvia, and producer Reg Hill to create a science fiction adventure series based on UFOs.

Some UFO episodes included serious adult themes such as divorce, drug use, the challenge of maintaining work/family balance, mind control, alien abduction, illegal organ harvesting, and murder.

Pinewood's studio buildings and streetscapes were used extensively in later episodes, particularly "Timelash" and "Mindbender" – the latter featuring scenes that show the behind-the-scenes workings of the UFO sets, when Straker briefly finds himself hallucinating that he and his colleagues are actors in a TV series.

[citation needed] The studio-as-cover concept served multiple practical and narrative functions: It was simple and cost-effective for the production, it provided an engaging vehicle for the viewer's suspension of disbelief, it eliminated the need to build an expensive exterior set for the SHADO base, and it combined the all-important "secret" cover (concealment and secrecy are always central themes in Anderson dramas) with at least nominal plausibility.

Comings and goings at odd times, the movement of people and unusual vehicles, equipment and material would not create undue interest and could easily be explained away as sets, props, or extras.

[1] The Andersons never explained at the time why female Moonbase personnel uniformly wore mauve or purple wigs, silver catsuits, and extensive eye make-up, and their unusual apparel is never discussed in the series.

Until not long before his death he possessed one of the wigs he wore on the show, and took great delight in displaying it at science fiction conventions and on TV programmes.

Most production miniatures typically consisted of a mixture of custom-made elements and detail pieces cannibalised from commercial scale model kits.

[18] Both Ed Bishop and Michael Billington commented that the futuristic cars were "impossible to drive", partly because the steering wheel was designed for looks rather than functionality.

The bodies were made of marine ply, fibreglass and perspex, built on a Mini Moke chassis incorporating an extra rear axle and modified by re-positioning the windscreen rearwards.

Miniatures from the series known to still exist include:[19] UFO confused broadcasters in Britain and the United States, who could not decide if it was a show for adults or for children.

[citation needed] Tony Jones of Starburst magazine gives the series a favourable review: "To a large extent, UFO is still very watchable [...] even if effects have moved on considerably in the past several decades.

[20] Paul Mounts comments that even if many episodes "seem ponderous by today's standards", the series is "really all about those extraordinary visuals, the thunderingly exciting Barry Gray signature music [...] thrilling title sequence [and] overarching scenario".

In 1972, a commentator for the Los Angeles Free Press wrote that UFO "plays like a combination of the worst traits of Batman and Star Trek".

"[23] According to a retrospective by Den of Geek, UFO "caught perfectly the depressive and fatalistic Zeitgeist of 1970s cinema, with relentlessly bleak endings and a hell of a lot of suffering on the way to them.

It mixed inventive scripting with frequently trite dialogue and vice versa; it put highly charged emotional, adult situations in the hands of actors who were often wearing absurd purple or platinum wigs [...] It kept you off-guard in a manner that few other shows have ever achieved, intentionally or otherwise."

In an article for Cinema Retro, Tim Greaves writes that UFO was the Andersons' first step "towards something aimed at a more mature audience, its storylines touching upon some distinctly adult themes.

Not only was there the ever-present core threat of aliens abducting humans and harvesting their organs to sustain their dying race; there were flirtations with adultery, divorce, interracial romance and the recreational use of hallucinogenic drugs [...] The very appearance of the aliens was disconcertingly sinister, sporting eerie liquid-filled helmets [...] Additionally, the characters regularly made flawed decisions and not all the stories concluded happily.

Many stations which carried the series were affiliated with CBS; they tended to schedule the show in the Saturday evening hour leading into All in the Family, the hugely popular comedy which was the highest-rated program on all of U.S. television at the time.

As the Moon-based episodes appeared to have proven more popular than the Earth-based stories, ITC insisted that in the new series, the action would take place entirely on the Moon.

The classic Dinky die-cast range of vehicles featured robust yet finely finished products, and included Straker's futuristic gull-winged gas turbine car, the SHADO mobile and the missile-bearing Lunar Interceptor, though Dinky's version of the interceptor was released in a lurid metallic green finish unlike the original's stark white.

[31][32] It was claimed that the UFO movie would be visual effects supervisor Matthew Gratzner's directorial debut[33] and that Joshua Jackson would play Colonel Paul Foster.