US preacher warns end of the world is nigh: 21 May, around 6pm

At about 6pm, he reckons 2 per cent of the world's population will be immediately "raptured" to Heaven; the rest of us will get sent straight to the Other Place.

If Mr Camping were speaking from any normal pulpit, it would be easy to dismiss him as just another religious eccentric wrongly calling the apocalypse. But thanks to this elderly man's ubiquity, on America's airwaves and billboards, his unlikely Doomsday message is almost impossible to ignore. 

Every day Mr Camping, an 89-year-old former civil engineer, speaks to his followers via the Family Radio Network, a religious broadcasting organisation funded entirely by donations from listeners. Such is their generosity (assets total $120m) that his network now owns 66 stations in the US alone. 

Those deep pockets were raided to allow Family Radio to launch a high-profile advertising campaign, proclaiming the approaching Day of Judgement. More than 2,000 billboards across the US are adorned with its slogans, which include "Blow the trumpet, warn the people!". 

Mr Camping, who makes programmes in 48 languages, boasts tens of thousands of followers across the globe, with radio stations in South Africa, Russia and Turkey. After 70 years of studying the Bible, he claims to have developed a system that uses mathematics to interpret prophesies hidden in it. He says the world will end on 21 May, because that will be 722,500 days from 1 April AD33, which he believes was the day of the Crucifixion. The figure of 722,500 is important because you get it by multiplying three holy numbers (five, 10 and 17) together twice. "When I found this out, I tell you, it blew my mind," he said. 

Recent events, such as earthquakes in Japan, New Zealand and Haiti, are harbingers of impending doom, he says, as are changing social values. 

Critics point out that this isn't the first time Mr Camping has predicted the second coming. On 6 September 1994, hundreds of his listeners gathered at an auditorium in Alameda looking forward to Christ's return.