A EuroMillions player in Birmingham has won £1m but has yet to claim the prize, the National Lottery has said.
The winning ticket was bought in Hodge Hill for the draw on 27 July and the winner has until Wednesday to claim the prize.
For every EuroMillions line played, UK players automatically receive a Millionaire Raffle selection printed on their ticket.
The winning selection on that day was DZL787851.
Simon Horne from the National Lottery said: "The clock is really ticking for someone to claim the prize.
"The ticket was bought for the draw which took place on the night of the opening ceremony of the London 2012 Olympics.
"We are still hopeful that someone will come forward at the very last minute to claim the money, which could really change someone's life."
If no-one comes forward with the winning ticket before the Wednesday deadline, then the prize money, plus all the interest it has generated, will go to The National Lottery Good Causes, Mr Horne said.