The prize, at least six times larger than any other sum of money won in a game of chance in Britain, represented the previous week's jackpot, which no-one had won, "rolled over" into last night's draw.
"This must be the largest Christmas present in history," said David Rigg, communications director of Camelot, the lottery operator.
The six jackpot numbers were drawn as: 26, 47, 49, 43, 35, 38. The bonus number was 28.
Today will see a frenzy of media activity in the search for Britain's biggest instant millionaire, and a flurry of calculations about just what £17.5m will buy. One suggestion last night: the Royal Yacht Britannia, as the Queen may be getting a new one.
A Camelot spokesman said: "One person is believed to have won £17.5m; another 10 have won between £250,00 and £300,000 each; and 680,000 people are winners."
The company refused to say where the winning jackpot ticket had been sold. The winner has a right to remain anonymous. "Until they come forward and claim the prize we must honour that right," a spokesman said.
Confirmation of the results was expected later today, he added.
Last night's jackpot had been estimated at £15m at the time of the live BBC draw, but was later revised after ticket sales were collated. Ticket sales, up 20 per cent on Friday of the corresponding day last week, exceeded 60 million for the first time after a last minute rush by people eager to cash in on the giant jackpot. Queues had been the order of the day at shops nationwide. People had made an "unbelievable" late dash for tickets, with queues at outlets stretching on to streets in towns across thecountry. Over £25m worth of tickets were believed to have been sold yesterday alone. "For two hours, we were selling £50,000-worth a minute," said the Camelot spokesman.
Tickets were in such demand at a petrol station in Hexham, Northumberland - the only outlet for miles - that at one point it ran out of tickets and owners considered turning off the shop computer to stop lottery fever affecting other business.
The prize fund for last night's draw, held in Belfast, was £34.5m.
The largest lottery prize ever won is believed to have been $111,240,463 and 10 cents, (about £71m) scooped by Leslie Robbins and Colleen De Vries, of Fond du Lac, Wisconsin, USA, for the Powerball Lottery on 7 July 1993.Reuse content