A chastened Josef Ackermann told a Düsseldorf court yesterday it "never came into my mind" that €57 million in bonuses paid to managers as part of Vodafone's takeover of Mannesmann six years ago might have been illegal.

Six years ago, the chief executive of Deutsche Bank headed the supervisory board of Mannesmann that approved the bonuses when the British mobile giant completed its hostile takeover of the century-old German company.

Mr Ackermann, former Mannesmann chief executive Klaus Esser and other supervisory board members were found not guilty two years ago of breaching fiduciary trust in approving the bonuses.

However, an appeal court judge threw out that ruling last year, sending the entire case back to where it started: chamber 111 in Düsseldorf district court.

The endless court appearances have been the real trial for the Swiss-born bank chief who knows that, as he sits in the Düsseldorf court for the second time, his successors are lining up in Frankfurt.

Two years ago, he turned public opinion against him by announcing in court that Germany was "the only country where people who successfully create value have to go to court".

Yesterday, he softened his words if not his intention.

"To this day, it is inexplicable to me that these bonuses are the starting point for a trial," he said. "If I had heard any legal qualms from any quarter, I would have not decided this way."

Mr Ackermann said the bonuses paid were "special compensation for extraordinary performances" of managers who had built up Mannesmann, and to guarantee a smooth integration into Vodafone. "It was a signal for the end of the hostilities of the takeover battle and for the dawn of a new era," he said.

That was cold comfort for Mannesmann shareholders at the back of the courtroom who tell familiar tales of telecoms shares that were talked up then plunged to a fraction of the purchase price.

"I don't know how these managers think they increased value - it was all hot air. At least 70 per cent of what I invested is gone," said Erhardt Knipping.

Many shareholders resent the "creating value" defence of the bonuses from managers who, in the heat of the dotcom era, sold off for one deutschmark Mannesmann's core engineering business, worth around several billion euro today.

In court, former Mannesmann chief executive Klaus Esser spent over 90 minutes defending his €15 million bonus. "I didn't ask for this bonus, I didn't demand this bonus and, least of all, I didn't decide on it," he said, reading a prepared speech.

He said he had "no reason to assume" the bonus "was motivated by anything but hard-headed judgment".

Mr Esser complained of "a media campaign where many untrue allegations have more influence than the reality", in particular the unproven allegation that the bonuses were agreed beforehand as the price for Mannesmann conceding to the takeover.

Düsseldorf lawyers watching the trial yesterday predicted that the defendants were likely to be found not guilty but only after a long and drawn-out trial.

"The judges know this isn't just about legal arguments but also the societal and political mood against excessive executive pay," said one lawyer. "The judges will want to avoid a quick case that would give the impression that the big boys just walk free, even if they will in the end. But for a man of position like Josef Ackermann it's almost worse to endure a long trial - that's his punishment."