Few cabinet ministers have been bombarded so persistently and savagely by their political opponents about their business activities as Mr Geoffrey Robinson, the man who lent Mr Mandelson the money to buy his house.
A multi-millionaire, Mr Robinson had barely been heard of outside Westminster, even though he had been an MP since 1976, until Mr Blair appointed him Paymaster-General after the last election.
From that moment Mr Robinson's name has been in the headlines: hardly ever for his ministerial achievements, but invariably for business deals, offshore trusts and what the Tories called his "tangled web" of commercial interests. Mr Robinson appeared unmoved by this ceaseless barrage.
Mr Blair refused calls to sack him, insisting he required evidence before disciplining a minister. Even so, he considered ditching him during his July reshuffle, but succumbed to Chancellor Gordon Brown's insistence that he stay.
No sooner had Mr Blair promoted Mr Robinson than the questions started coming, first about his business association with Joska Bourgeois, a wealthy Belgian divorcee who died in 1994 aged 81, and who set up a Guernsey-based trust for his family. There followed an avalanche of press reports about all manner of business arrangements.
But Mr Robinson remained unabashed, even amid accusations of hypocrisy that he was reducing tax allowances for ordinary investors, while benefiting from offshore tax breaks himself.
In November this year he was compelled to apologise in the Commons for failing to register a directorship. But the apology lasted less than 60 seconds, and its brevity infuriated MPs, including some Labour ones, who under the rules could not question him.
Mr Robinson was born on May 25th, 1938, into a Labour-voting family and remembers delivering envelopes in Balham, south London, in the 1945 election. He won a scholarship to Emanuel School, London, another to Cambridge and finally to Yale. By the time he was 33 he was chief executive of Jaguar Cars, the prototype whizz-kid.
In 1976 he won a by-election in Coventry North West, home of the two Jaguar plants.
His wife, Marie, a successful Italian opera singer, has not been enthusiastic about his political career, saying: "I don't think I should follow him like a little dog."
Having entered the millionaire class, Mr Robinson bought the ailing left-wing New Statesman magazine, but not because he thought it would be a good investment. "You would need to be certified if you thought you were going to make money out of it," he laughed.