The largest mobile operator in Europe, Mannesmann already controls the biggest German mobile group, D2, and on Tuesday completed the acquisition of Olivetti's stakes in Italian mobile operator Omnitel and fixed-line operator Infostrada.
"Britain is an important market and One2One is one of the opportunities there," said Klaus Esser, Mannesmann chief executive, adding that the UK is a big "hole" in the group's European coverage. He said Mannesmann was considering other avenues to tap the British market and is looking to build presences in Spain and Switzerland.
Sources close to One2One said Mannesmann is one of a handful of remaining bidders, understood to include Deutsche Telekom, France Telecom and Vivendi. Telecom Italia Mobile, now controlled by Olivetti, is believed to have dropped out.
However, analysts discounted the likelihood of Mannesmann winning One2One. "We don't think Mannesmann is the most likely buyer," said Chris Godsmark, telecoms analyst with Investec Henderson Crosthwaite. "The most likely buyer remains Deutsche Telekom or France Telecom."
Earlier this year One2One owners Cable & Wireless and MediaOne Group of the US put the mobile company up for sale. Last month C&W mortgaged its half share for pounds 3.8bn in cash to a new finance company owned by itself, financial advisor Merrill Lynch and a trust company.
In addition to its market-leading German and Italian subsidiaries, Mannesmann is a 15 per cent shareholder in French mobile network Cegetel and part owner of a mobile network in Austria.
Mr Esser's determination to take control of One2One is something of a blow for Vodafone, which had hoped to build a closer relationship with the German company. Through its impending pounds 38bn takeover of AirTouch, Vodafone will inherit a minority stake in D2.
Analysts said a successful Mannesmann bid for One2One would probably work against the German group entering a strategic alliance with Vodafone. It would also be likely to stall any near-term development of business synergies between the companies.
The sale of One2One, expected to be finalised by mid-July, could unleash a series of mobile deals in Europe. This could see minority shareholders bought out, while rising players, such as BT, Vivendi and Vodafone, expand their holdings.
Mobile shareholding structures are "all very convoluted," said Salomon Smith Barney analyst John Jenson. "At some point, the minority stakes will have to be ironed out."