LONDON (Reuters) - The winners of Britain's biggest lottery prize, worth 91 million pounds, will break their silence on Tuesday to explain how they plan to spend their windfall, organisers said on Monday.

Lottery operator Camelot said the prize will be split between a married couple from south Wales and a group of computer workers from Liverpool who picked the winning numbers as a syndicate. It was not known how many were in the syndicate.

They will each pick up 45.5 million pounds after matching the winning numbers in Friday's EuroMillions draw, a lottery played in nine European countries.

The winning numbers were 11, 19, 34, 43 and 45 and the Lucky Numbers five and nine. Jackpot winners must pick all five main numbers and the two extra numbers. Each ticket costs 2 pounds.

The IT staff work for U.S. company Hewlett Packard, while the married couple live near Newport in south Wales. They will be named for the first time at two news conferences.

In May, a lottery player in Spain won 126 million euros (113 million pounds) playing EuroMillions in what was believed to be Europe's biggest ever lottery win for a single ticket.

(Reporting by Peter Griffiths; Editing by Louise Ireland)