The player had until Monday evening to claim the money, but did not come forward by the deadline.

Winners have 180 days to claim. The ticket, bought on 28 September 2005, matched five numbers and the Thunderball, but now the cash goes to the lottery's good causes.

Camelot said it was a shame for the winner, but the nation would benefit.

A National Lottery spokesperson said: "Unfortunately, I can confirm that the ticket-holder did not come forward within the deadline to claim their prize and has now sadly missed out on this substantial amount of money.

"To avoid this unfortunate situation happening again, I would urge all National Lottery players to check their tickets on a regular basis.

"We tried very hard to find the ticket-holder and it's a real shame that they have missed out, but there is still one winner - the nation.

"This money will now go to the good causes, adding to the £18bn which, over the last 11 years, has funded the biggest programme of civic regeneration seen in the UK since the 19th Century."