One lucky Lottery winner is sitting on a pot of gold - and has just one week left to cash in the EuroMillions ticket, which is worth £63,837,543.60.
If the prize is not claimed by 11pm next Wednesday December 5, the ticket, which was bought in the Stevenage and Hitchin area for the EuroMillions draw on Friday June 8, will expire.
The all-important numbers on that date were 5, 11, 22, 34, 40 and the Lucky Star numbers were 9 and 11. The missing ticket-holder matched all five main numbers and both Lucky Star numbers.
If nobody comes forward to claim the prize, the money, plus all the interest it has generated, will go to the National Lottery Good Causes - adding to the £29 billion already raised through sales of lottery tickets since the National Lottery launched in November 1994.
With the deadline fast approaching, the National Lottery has appealed to all lottery players to check their tickets to see if they are the mystery prizewinner.
A National Lottery spokesman said: "Whilst we've done a huge amount of activity to raise awareness of the prize, and we're using the ad vans this week to make sure as many people as possible get the message again, we're still waiting to pay the money out to the rightful ticket-holder.
"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."
Advertising vans displaying important information will be touring Stevenage and Hitchin this week, while retailers will be displaying posters up until the last minute to remind their lottery-playing customers to check their tickets.
The National Lottery has already been raising awareness using a town crier in a Lamborghini and visiting Luton airport to remind those returning from holiday to check their tickets.
Anyone who believes they have the winning ticket for any of the draws within the 180-day deadline should call the National Lottery Line on 0845 910 0000.