In 1990 Spy magazine published a 'scientific' study on Santa. With 300,000 animal species still to be classified they didn't rule out the possibility of flying reindeer. However, their calculations about Santa's big night weren't so encouraging.

Excluding those religions that don't go in for Christmas, they calculated that Santa had to deliver presents to 378 million children in 91.8million homes. Travelling east to west, he would have 31 hours to do his work.

Santa would have a mere 1/1000 of a second to stop at each home, shin down the chimney, fill the stockings, eat the mince pie, shimmy back up the chimney and get the sleigh moving to the next home. He'd have to cover 75.5 million miles at and average speed of 650 miles a second – 3,000 times the speed of sound.

Taking the average present to be a 1 kilo Lego set, the slight's payload would be 350,000 tons, four times the weight of the QE2. Travelling at 650 miles per second the air resistance would cause the lead reindeers to absorb 14.3 quintillion Joules of energy. They'd instantly burst into flame and cause horrendous sonic booms while Santa, not th fittest of individuals would be subjected to 17,500 times the force of gravity, pinning him to the seat with a force of 4.3 million pounds.

The world's scientists instantly gave up searching for cold fusion and their car keys and turned their minds to the Santa problem. Dr Arnold Pompos of high-energy physics research facility Fermilab found an answer that also solved the question of Rudolph's nose. Astronomers measure speed with the Doppler Shift, (colours change the faster a body moves as the light waves catch each other up), Rudolph's red nose would change colour as he accelerated, first turning yellow, then green, then blue, the violet before becoming invisible. Dr Pompos reckons Santa travels at 99.99999 per cent of the speed of light.

Dr Roger Highfield, science editor of the Daily Telegraph, thinks that Santa has heat shields to protect himself as well as warp drives. "The Spy magazine allegation is outrageous," he said. We know Santa delivers those presents on Christmas Eve as reliably as we know Rudolph's nose is red."

And then, presumably, yellow, green, blue, violet and invisible.

Extract from Stuff the Turkey by Steve Caplin and Simon Rose, published by Simon & Schuster, November 6th £9.99