A Lotto ticket-holder is yet to claim their £5 million jackpot prize a week on from the draw.
The winner bought their ticket in a shop rather than online, operator Camelot said.
The winning Lotto numbers in the September 28 draw were 3, 15, 20, 48, 57 and 58.
Camelot urged players to check their paper ticket either in store or by scanning it via the National Lottery app.
Andy Carter, senior winners’ advisor at The National Lottery, said: “Have you got an unchecked Lotto ticket? Well, it could be life changing. Players should check their tickets and contact us so that we can pay out another fantastic Lotto jackpot prize.
“It’s been a busy month or so for me and my team with Lotto making an amazing 14 millionaires since the beginning of September and we hope this lucky Lotto streak continues.
“Each and every winner has a chance to change their life and the lives of the people around them, whether that be with homes, holidays or supporting causes close to them.”
If no valid claim has been made on the prize by around two weeks after the draw, Camelot will reveal the general area in which the ticket was bought to encourage tickets to be checked but to allow the winner to remain anonymous if they wish.
Once a ticket-holder has called Camelot and a claim has been validated and paid, the ticket-holder will then decide whether or not to go public.
There will be no information on whether the winner is an individual or a syndicate unless the ticket-holder decides to go public.
With all National Lottery draws, players have 180 days from the day of the draw to claim their prize if they have the winning ticket.
Anyone who believes they have the winning ticket should call the National Lottery Line on 0333 234 5050 or email firstname.lastname@example.org.