Banker Nathaniel Rothschild yesterday sought "substantial libel damages" at the High Court because of what he claimed were "sustained and unjustified" attacks by the Daily Mail.
Closing the case for the Swiss-based financier yesterday, Hugh Tomlinson QC told Mr Justice Tugendhat in London that a May 2010 article bore serious defamatory meanings to which Associated Newspapers had no defence.
He said that the failure to offer any correction or apology and the persistence in a plea of justification had caused 40-year-old Mr Rothschild distress and additional damage for which he was entitled to be compensated.
Rothschild said he was "incredibly upset and distressed and amazed" when he saw the story which, he claimed, portrayed him as a "puppet master" who had brought together Lord Mandelson, then a European Trade Commissioner, and Russian oligarch Oleg Deripaska, in January 2005. He dismissed it as "fiction".
Tomlinson told the judge, who heard the four day case without a jury, that Rothschild regularly approached major institutions to raise considerable sums of money and his integrity was "absolutely crucial" to him.
"The idea that he is playing dubious games with a European trade commissioner to impress Mr Deripaska, in circumstances where it is suspected they are up to no good over aluminium tariffs, is an extremely damaging one," he said.
The case for the newspaper, he said, was that Rothschild took Lord Mandelson on a trip to Siberia in order to impress Deripaska when he knew, or ought to have known, that if anyone found out about it, Lord Mandelson would have been compromised.
He added that it was also said there were grounds for believing that Lord Mandelson discussed aluminium tariffs with Deripaska and Rothschild encouraged the inappropriate relationship.
Tomlinson said the evidence demonstrated that the trip was a "purely recreational one", disclosed to and approved by Lord Mandelson's office and not giving rise to any actual conflict of interest.
It was important to bear in mind that in 2005, Lord Mandelson was a long-standing friend of Rothschild while Deripaska was also a friend and someone he had no need to impress.
Rothschild had no awareness of aluminium tariffs and how they might impact upon Deripaska's business and no knowledge of the rules by which EU Commissioners were bound, he added.
Trip was 'purely social'
Counsel said the newspaper contended that the article was very much focused on Lord Mandelson, who it described as an experienced politician, well capable of making his own judgments as to what was or was not appropriate.
"That deals a fatal blow to any attempt to criticise the claimant for inviting his friend Lord Mandelson on the trip."
Lord Mandelson and Deripaska were not parties to the action and did not take any part in the trial.
Tomlinson emphasised that the case was not about them and the newspaper made no allegations they had done anything wrong.
"It is not said that Lord Mandelson had in fact a conflict of interest - simply there was an appearance.
"It is not said that Lord Mandelson failed to make any declarations of interest that he ought to have made or anything of that sort."
Rothschild said in evidence that the presence of Lord Mandelson on the overnight trip to Abakan - together with Rothschild, another friend, Sebastian Taylor, Peter Munk, chairman of Barrick Gold, and Deripaska, who had a chalet nearby - was "purely social".
It took in a visit to a smelter facility and its museum, a banya - a Russian-style sauna - skiing, five-a-side football, ice-hockey, Russian billiards and entertainment by a Cossack band.
He added: "No EU tariffs or other matters of that nature were discussed. The only business was to take place in Central Asia, after Lord Mandelson had returned to Brussels."
Tomlinson referred to evidence given during the hearing by Conservative Party co-chairman Lord Feldman, who had been served with a witness summons by Associated Newspapers.
Lord Feldman said that, during a holiday on Corfu in August 2008, Rothschild suggested that Deripaska could be interested in making a party donation.
But Rothschild said he had a different recollection of events and made it clear that he stood by the contents of his letter to the Times on the subject in October 2008.
Tomlinson said that there was a "difference of recollection and emphasis" between Rothschild and Lord Feldman relating to a "social conversation" which was fleeting in nature.
"There were honest differences of recollection, emphasis and interpretation in relation to the conversations about donations which took place."
'An action about reputation'
In his closing speech, Andrew Caldecott QC, for Associated Newspapers, said that the defence of justification should succeed as it was "clear beyond doubt" that the article meant there was a "wider malaise", and that aspects of the trip made good the "central sting".
Rothschild fostered a relationship between Lord Mandelson and Mr Deripaska which endangered the dignity and reputation of Lord Mandelson's office by bringing him inappropriately close to Deripaska, he added.
"This is not an action about accuracy. It is an action about reputation," he said.
Caldecott said that three of the people on the trip - excepting Lord Mandelson and Taylor - were joint venturers.
"It was a business trip for them. There were some discussions on the Siberia leg before they went on to Asia," he continued.
He said that the hospitality provided by Deripaska included a private jet flight from Moscow to Siberia, transport, wining and dining.
The extreme brevity of the trip, the four-hour flight, the temperature of 25 degrees below, all invited the outsider to think there was a "keenness" to meet Deripaska.
"All these were the results of Rothschild's invitation to Lord Mandelson and the effect is cumulative as well as individual," he said.
Caldecott said that influence "can be subliminal as well as overt".
He added: "It is way beyond the norm for a Russian oligarch to be flying the trade commissioner, who he does not know well at the time, to fly him in his private jet to his private chalet to be wined and dined by him.
"It creates the perception that Lord Mandelson may be beholden to his host and also gives Mr Deripaska cachet."
He said there was no dispute that Deripaska was a man "who has been and is interested in political influence".
Caldecott said that Rothschild must have known that they were setting out to stay with Deripaska and that he would be providing the hospitality.
The idea that they were Rothschild's guests and not Deripaska's was "wholly unsustainable".
"One would say 'to whom would one write the thank-you letter?' If you did not write to Mr Deripaska, it might be thought to be slightly discourteous."
He said that the heart of the purpose of the trip was plainly to allow Mr Deripaska to get to know Lord Mandelson better, and the newspaper said that was inappropriate.
Caldecott said that it was accepted that there were recreational moments to the trip, but said the court should be wary of the photos it had seen, which Rothschild said showed a "light hearted and enjoyable visit" by friends.
"Businessmen discuss business on ski lifts - and when they are having banyas. You may have a recreational background to a business discussion," he said,
The judge stated he would give his ruling at a later date.
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