The ticket was bought in March this year
Posters are being put up in parts of Worcestershire to try to trace the owner of a winning lottery ticket.
The ticket, bought in the Malvern and Worcester area, contains the numbers of 6, 9, 20, 21, 31, 34, and was drawn on 11 March yielding a jackpot of £2.5m.
The owner of the ticket has until 7 September to claim their prize and if the deadline passes the money will go to the lottery's Good Causes scheme.
People are being urged to check their wallets and old tickets.
"We have the champagne on ice and our fingers crossed that the lucky winner, wherever they are, comes forward to claim their win," a lottery spokesman said.
Anyone who believes they have the winning ticket is urged to call the National Lottery Line.