Update | Peter Higgs and Francois Englert win Nobel for 'God particle' theory

Britain's Peter Higgs and Belgium's Francois Englert won the Nobel Prize for Physics for conceiving of the so-called "God particle".

Higgs, 84, and Englert, 80, were honoured for theorising a particle - discovered last year after an agonising quest - that explains why the universe has any substance at all.

"Without it, we would not exist, because it is from contact with the field that particles acquire mass," the jury said in a statement.

The announcement was delayed by one hour, which is highly unusual. The academy gave no immediate reason, other than saying on Twitter that it was "still in session" at the original announcement time. The academy decides the winners in a majority vote on the day of the announcement.

The delay drew a joking reaction from Englert. "I thought first I had to make a very low festivity because I didn't see any announcement," he said. "But now I'm very happy."

Staffan Normark, the academy's permanent secretary, declined to explain the delay. He said the committee could not get directly in touch with Higgs to inform him of the prize.

"Actually, we tried quite hard to get a hold of him, but of all the numbers we tried, he didn't answer," Normark said. The committee had to send him an e-mail instead.