In keeping with the spirit of Christmas the North American Aerospace Defence Command (Norad), based under Cheyenne Mountain in Colorado, will be tracking Santa's sleigh on Christmas eve and displaying his progress on its Santa website. 

Billions of dollars worth of high-tech radar equipment in stations spread across the US and Canada will follow Santa on his route around the globe before finishing the job in Hawaii on Christmas morning.

Santa will have a military escort for much of his flight. "Canadian Norad fighter pilots, flying the CF-18, take off out of Newfoundland to intercept and welcome Santa to North America," says the site.

"Then at numerous locations in Canada other CF-18 fighter pilots escort Santa, while in the US American Norad fighter pilots in either the F-15 or F-16 get the thrill of flying with Santa and the famous reindeers Dasher, Dancer, Prancer, Vixen, Comet, Cupid, Donner, Blitzen and Rudolph."

About a dozen Norad fighters in Canada and the US are equipped with Santa Cams, and intelligence from previous tracking missions has revealed that Santa has "a generous girth, rosy cheeks from sleigh riding in cold weather, and a flowing white beard and hair".

However, there may be a more sinister explanation for Norad's interest in the Arctic toys and coal distributor.

Professor Nils Lid Hjort, from Oslo University's mathematics department, has suggested to science website Physorg that Santa could be colluding with the defunct East European secret police in order to carry out his rounds. 

"The STASI archives are still secret, and this is a clear indication that information about nice and naughty children is there," he said.

The professor does not rule out co-operation with local security services, which often have the latest information on whether a child is good or bad.