BBC:

UK election exit poll predicts Conservatives will be largest party in a hung parliament, with 316 seats to Labour’s 239. Survey by NOP/Mori for BBC, ITV and Sky.

If this is (more or less) correct — and the math is unusually difficult this year — this is a very big surprise indeed. The Conservatives would (one way or another) be able to hang on.

Update: The Sun rains on the parade:

David Cameron and Ed Miliband will both fall well short of outright general election victory – plunging Britain into weeks of political chaos, an exclusive exit poll for The Sun has revealed.
The massive YouGov survey of how 6,000 people voted across the country today has revealed NO last minute surge for any party.
It found the Conservatives and Labour are still tied on 34%, with UKIP on 12%, Lib Dems 10%, the SNP and Plaid on 5% and the Greens on 4%.