A mystery lottery winner had until 11pm on Wednesday to claim a £64m prize before the ticket expired.
The EuroMillions ticket was bought in the Stevenage and Hitchin area of Hertfordshire for the draw on Friday, June 8. The jackpot is worth a cool £63,837,543.60.
It was unclear on Wednesday night whether someone had come forward at the last minute to claim the prize.
The National Lottery has been searching for the lucky holder through adverts and posters in the area, and even using a town crier proclaiming the win from a Lamborghini.
The missing ticket-holder matched all five numbers - 5, 11, 22, 34 and 40 - and both Lucky Star numbers - 9 and 11.
All lottery players have been urged to check their tickets and perhaps even search some of the more unusual places where "lost" tickets have been found in the past.
Top spots where tickets have been discovered include down the back of the sofa, in a car sun visor and more unusually inside a tin of cat treats.
Number one spot was in a bin bag that was about to be collected, according to anecdotal evidence from the National Lottery.
If the prize goes unclaimed, the money, plus all the interest it has generated, will go to the National Lottery Good Causes.
"Our message is simple - we're urging everyone to look one last time everywhere a missing ticket could be hiding," said a National Lottery spokesperson.
"We're desperate to find this mystery ticket-holder and unite them with their winnings - this amazing prize would be a fabulous early Christmas present."