Prime Minister David Cameron is to step down by October after the UK voted to leave the European Union.
Mr Cameron made the announcement in a statement outside Downing Street after the final result was announced.
While England voted overwhelmingly for Brexit, Scotland and Northern Ireland backed Remain. Statements are expected to be made by Sinn Fein and the SNP later today calling for a breakaway from the Union. London backed Remain but the turnout was lower than expected because of bad weather.
The pound crashed to the lowest level since 1985 as sterling fell below $1.35. Complacency about a Brexit outcome will come clear this morning, as out of hours trading suggests that the FTSE 100 will drop by 8.8pc, or by some 560 points. The fall would be the third worst in history if stocks ended the day down as sharply.
Oil prices slumped by more than 6 percent on Friday after results of a landmark referendum showed Britain had voted to leave the European Union, causing huge market uncertainty and fracturing European efforts to forge greater unity.
The dollar fell below 100 yen for the first time since November 2013, while the pound dropped by the most in living memory.
U.S. crude CLc1 was down $2.77 at $47.34 a barrel at around 0314 GMT. Brent crude LCOc1 was down $2.75 at $48.16 a barrel.