Tony Paterson: From Big Brother ... to Foreign Minister

Coming from the man expected to become Germany's foreign minister, it was an enlightening foretaste of a new Teutonic assertiveness in international affairs: Guido Westerwelle refused to answer a question in English at his debut press conference.

"Would you be so kind, this is ... Germany," said the permatanned Mr Westerwelle. "In Great Britain people are expected to speak English and it is the same in Germany, people are expected to speak German."

In the end, the unfortunate BBC reporter was forced to use a translator. Mr Westerwelle is no stranger to eccentric, even obstinate behaviour. He is the only German politician to have appeared on Big Brother and is renowned for trying to win votes with a bizarre form of canvassing called "fun politics".

The 47-year-old gay leader of the Free Democrats swept his pro-business party into government in Sunday's general election. His party will share power with Chancellor Angela Merkel's conservatives and as leader of the junior coalition partner, Mr Westerwelle will automatically assume the job of Vice-Chancellor.

His transformation from BB housemate to minister has not happened overnight. It has been 11 years since the Free Democrats were in office and Mr Westerwelle has got them there the hard way. His "fun antics" – painting 18 on the soles of his shoes to represent the share of the vote he wanted, and touring the country in a bright yellow bus or "Guidomobile" – were regarded with suspicion by most Germans and distracted from the party's neo-liberal, pro-market policies.

But the past four years have seen Mr Westerwelle jettison his clowning persona in favour of a far more serious approach. By targeting Mittelstand or medium- sized companies with the promise of tax cuts, he has secured a record number of votes (14.6 per cent, just off the shoe dream).

"Of course I made some mistakes, but one grows older and wiser," he said in an interview ahead of the poll – an interview, it should be noted, that was conducted in Deutschland and delivered in faultless Deutsch.