London stock exchange
The Worldpay IPO is set to be the biggest of 2015Getty

Payment processing firm Worldpay is offering its shares at 240p each, valuing the company at around £4.8bn, in the biggest London floatation of 2015. The British company announced its estimated market cap on Tuesday (13 October), almost completely in line with expectations.

The initial public offering (IPO) is expected to raise between £2.16bn and £2.48bn for Worldpay, with it floating two billion shares, or 45% of the company.

"We have already invested over £1bn in our technology, people and capabilities, helping us to become an advanced and sophisticated technology-led organisation with great potential," chief executive Philip Jansen said. "We welcome our new investors and thank them for the strong interest they have shown in the offer."

Jansen is expected to land a £50m perk from the floatation, it was revealed in September. In a pay-out across management worth £350m, several top dogs at the booming payment processor will be made millionaires after the IPO.

Rather than accepting a £6.6bn takeover offer from French rival Ingenico, Worldpay opted for a floatation, which would see it join the likes of Fitbit as one of the biggest IPOs in 2015.

The offering will probably even be the biggest on the London Stock Exchange of the year, and it will send the company straight to being one of the FTSE 100's biggest listed companies.

Worldpay has listed Merrill Lynch, Goldman Sachs and Morgan Stanley as advisers and cooperators to assist with the float. The company, founded in 1997, was owned by private equity groups Advent International and Bain Capital.

"Worldpay managed to list this morning at 240p, right in the sweet spot of an initial 225p-260p marketing rage which was subsequently narrowed to 235-250p," Michael van Dulken, head of research at Accendo Markets, said. "It currently trades at 250p equating to a positive market debut in light of a slower pace of listings and a cooling in appetite for new paper over the last two years following Foxtons and Royal Mail induced excitement."