Here's to Eternity

Eternity captured 20% of the British board game market within a month of its release It features 209 jigsaw pieces which have between seven and eleven sides All are the same colour and can be used on either face Unlike normal jigsaws, there is no pattern or picture to follow

"I decided to use a computer but to give it a lot of help along the way.

'Blind alley'

"First we worked out the difficulty of each piece using a probability model. We then programmed the computer to start work on the harder pieces first.

"It took about two weeks to decide on the most promising possibilities.

"We then constantly improved and refined the computer program, although we did go up a few blind alleys and were lucky to solve it so quickly."

Mr Selby solved the game with help from a former colleague, Oliver Riordan.

Mr Riordan, 28, is one of the world's top mathematicians, but is living in halls at Cambridge University while he carries out research there.

He will share the winnings with Mr Selby, and is planning to buy a new home with his money.

Mr Monckton - the brother of Rosa Monckton, a close friend of the late Diana, Princess of Wales - was convinced it would be at least three years before anyone solved the game.

By this time, he hoped to have made enough money to cover the prize fund, with the rest coming from an insurance policy.

But he said: "I'm delighted it's been solved."