SHARES in PartyGaming, the controversial internet poker company, soared by 11 per cent on their first day of trading yesterday in the biggest flotation of a British company for five years.

The company, whose shares added 13p to close at 129p, ended the day with a market capitalisation of £5 billion, putting it into the FTSE 100 ahead of British household names such as British Airways and ICI, the chemicals group.

The flotation, which did not raise any money, gave its four founders a combined windfall of about £797 million and valued their remaining shares at about £3.3 billion.

Anurag Dikshit, the group’s operations director, has made the most from the flotation, cashing in £394 million worth of his shares and retaining a 30 per cent stake worth about £1.4 billion at last night’s closing price.

Ruth Parasol and her husband, Russell de Leon, each made £202 million from selling part of their holdings, while they have retained stock worth about £1.5 billion at last night’s closing price.

Vikrant Bhargava, the company’s marketing director and fourth founder, saw his stake valued at close to £547 million in the flotation.

PartyGaming’s listing, which saw 20.6 per cent of its shares sold to insitutions, is the biggest in the UK since July 2000, when Dimension Data floated with a market value of £6 billion.

Richard Segal, PartyGaming’s chief executive, said: “We did not need to raise any money because we have strong cashflows. This will enable us to fund organic growth and to make acquisitions. We want to expand into new distribution channels, such as wireless, and to extend the brand.” Mr Segal said that he was “very satisfied” with PartyGaming’s debut, which has been mired in controversy for weeks. The issues raised during the process have ranged from the dubious legality of online gambling in the United States, PartyGaming’s biggest market representing about 80 per cent of its customers, to the background of Ms Parasol, who made her first fortune in internet pornography.

The offering, which was managed by Dresdner Kleinwort Wasserstein, was more than three times covered.

PartyGaming has shared some of its profits with staff, giving all 1,100 employees a combined 5.6 per cent stake in the company, worth about £220 million at the flotation price.