After a brief Orson Welles-style opening announcement, recalling Welles' notorious radio adaptation of The War of the Worlds, the programme begins with a 20th Century Fox fanfare.
The first 25 minutes take the form of a live "UFO watch" broadcast hosted by Radio 1 DJ Nicky Campbell and veteran TV astronomer Patrick Moore (of The Sky at Night) aboard an RAF Sentry aircraft.
When the alien mothership disgorges dozens of smaller ships that take up position over the world's cities, the broadcast switches to a press conference called by Prime Minister John Major and Opposition Leader Tony Blair to announce the formation of an emergency coalition government.
DJ Mark Goodier reports from a rooftop on the alien ship's approach to London until it fires its weapon and the broadcast goes silent.
After a brief pause the story continues in Maggs' trademark "audio movie" style, with original music from the film and sound effects and dialogue in Dolby Surround.