The Earth seems doomed, and the world is hoping against hope for salvation. To be honest it was an ambitious script for anyone to film convincingly, but Guest manages it, and the result is an engaging and surprisingly realistic thriller.

Edward Judd stars as a "Daily Express" hack who discovers the Earth has inadvertently been tilted off its axis by two simultaneous H-bomb tests, conducted separately by the USA and the USSR. The world is plummeting closer to the sun. The weather takes a horrific twist, and the planet starts to overheat.

Guest's strong direction ensures crisp pace throughout, and the use of a low-key, pseudo-documentary style and mock newsreel footage is extremely effective in building tension. Les Bowie's special effects are convincing - particularly considering the budget and technology available - and he successfully creates an atmosphere of apocalyptic terror as the Thames evaporates, and a terrified London swelters in fiery fog and heat.

The film is clearly a product of the menacing claustrophobia of the Cold War, and the political overtones of the period are obvious. The disaster is caused by the two superpowers simultaneously plotting their own plans for nuclear armageddon, and the film explores the absurd irony of a deterrent based on mutual destruction. Through the disaster the superpowers begin to co-operate - but will humanity get a second chance?

"The Day the Earth Caught Fire" is on BBC1, 12.50am, Friday 19th October.