A family who scooped the £61.1 million EuroMillions jackpot are to reveal how they will spend their fortunes on Wednesday morning at a press conference in Newport, south-east Wales.
The syndicate, from nearby Monmouthshire county, will talk about the life-changing win at the Celtic Manor Resort in the Usk Valley at 10.30am.
The relatives jointly claimed Friday's winning jackpot, which is the largest of the four to be won by UK ticket-holders this year.
Subject to validation, the £61,102,442.90 prize could be paid out when banks open on Monday, lottery operator Camelot said.
A National Lottery spokesman said: "What an amazing win for the UK - the fourth EuroMillions jackpot to be won here this year.
"We're delighted the ticket-holder has come forward to claim their prize and their ranking of 10th place in the National Lottery rich list."
Friday's winner matched five main numbers and two lucky stars. The winning numbers were 01, 21, 26, 40 and 50, while the lucky star numbers were 02 and 04.
As well as the jackpot prize, five players won a guaranteed £1 million and a luxury trip to Australia's Gold Coast in the UK Millionaire Maker, a National Lottery spokesman said.
The latest win comes after an unnamed UK ticket-holder claimed £51.8 million on EuroMillions in April, which followed jackpots worth £24.7 million and £24.6 million won by UK ticket-holders in February.
All three ticket-holders remained anonymous.
These big prizes are some way from being the largest for a UK winner. Colin and Chris Weir, from Largs, North Ayrshire, scooped a £161,653,000 EuroMillions jackpot in July 2011.