Boris Johnson and Sadiq Khan clashed tonight in Britain's biggest ever live political debate at Wembley Arena.
So great was the strain on the system that the official registration website crashed and the deadline was extended for 48 hours.
Provisional figures show 38,956,824 people are registered for Thursday’s poll in England, 3,988,492 in Scotland, 2,270,743 in Wales, 1,260,955 in Northern Ireland and 24,117 in Gibraltar.
It’s nearly 150,000 more people than the previous record of 46,354,197 who signed up to vote in last year’s general election.
And turnout will be key as young voters, who are more likely to be late signups, are more likely too to swing behind Remain.
The previous record for any UK wide election was the 46,487,579 voters registered at the European Parliamentary Elections in 2014, but more people are allowed to vote in these.
Three more Tory MPs have joined the remain camp, bringing the total by our tally to 186 - compared to 135 voting for Brexit.
Our analysis says just 13 MPs in the whole Houses of Parliament remain undeclared after Jackie Doyle-Price, Caroline Nokes and David Tredinnick stuck with In. The 13 MPs whose decision still isn’t public: Tories (9): Anne Milton, Caroline Ansell, Charlotte Leslie, Eleanor Laing (Deputy Speaker), Huw Merriman, Ian Liddell-Grainger, Jesse Norman, Pauline Latham, Tracey Crouch Labour (3): John Spellar, Lindsay Hoyle (Deputy Speaker), Natascha Engel (Deputy Speaker) Speaker (1): John Bercow The unexpected star of the BBC’s Wembley Arena TV debate was Scottish Conservative Leader Ruth Davidson.
Also for Leave was Tory minister Andrea Leadsom, who refused calls to return £600,000 given to Vote Leave by an ex-BNP member.
Earlier the Prime Minister set out his final arguments for why Britain should stay in the European Union, urging older generations to think about the future for their children and vote remain.