The draw took place on Tuesday, July 19.
The winning numbers were 6, 23, 27, 40 and 41 with the lucky star numbers being 2 and 12.
Why we may never know if the UK winner is from Sussex?
A spokesperson from Camelot UK Lotteries Limited, operator of The National Lottery, said once the ticket has been validated and paid, the ticket-holder will then decide whether or not to go public and share their news.
There will be no information on whether they are an individual or syndicate winner, or where the ticket was purchased, unless the ticket-holder decides to go public, according to the spokesperson.