The UK winner of the third biggest EuroMillions jackpot worth £123 million has yet to come forward to claim their prize.
Camelot has urged players to check, “double-check and triple-check” their ticket the firm raised concerns that the holder may not have realised they won.
A single ticket scooped last Tuesday's £123,458,008 prize pot - the third biggest in the draw's history.
It is not yet know whether the winner is an individual or a syndicate. Camelot could only reveal at this stage that the ticket was bought at a National Lottery retailer, rather than online.
However, the area where the ticket was bought will be revealed in around a week's time if no valid claim has been lodged by then.
The owner of the winning ticket matched all five main numbers and two Lucky Stars in the June 11 draw.
The winning numbers on that date were 25, 27, 39, 42 and 46, with Lucky Stars 11 and 12.
Andy Carter, senior winners' adviser at the National Lottery, said: "It seems this massive winner might not even be aware that they are one of the biggest National Lottery winners ever.
"A week has slipped by and winners may have been going about their everyday routine completely unaware of this amazing change of fortune.
"The ticket was bought in-store so players should check the places they usually keep their tickets and make sure they've checked them all. We have the champagne on ice and our fingers crossed that the lucky winner comes forward to claim their win soon.
"Our player services team are on stand-by waiting to meet the lucky winner or winners. They have great expertise in helping winners embrace life-changing wins and making sure that they are able to start to enjoy their new found wealth as quickly as possible.
"They will be on hand every step of the way to guide the ticket-holder through the winning experience."
This is the fourth EuroMillions jackpot win in the UK this year.
Patrick and Frances Connolly, from Northern Ireland, won £114.9 million in the EuroMillions New Year's Day draw, Ade Goodchild, from Hereford, banked £71 million in March, and an anonymous ticket-holder scooped £35.2 million in April.