Daniela Weber, WPP Italy's chief operating officer, used her affair with WPP boss Sir Martin Sorrell to strengthen her position at the group, a court was told today.

Ms Weber's relationship with Sir Martin was common knowledge at the company's Milan office, Monica Mormina, a former manager at WPP Italy, told the high court in London. Ms Mormina gave evidence through an interpreter on the seventh day of the libel trial Sir Martin is bringing against two former Italian colleagues: Marco Benatti, WPP's former "country manager", and his lieutenant Marco Tinelli.

Under cross-examination by Sir Martin and Ms Weber's barrister, Desmond Browne QC, Ms Mormina was asked whether she disliked Ms Weber.

"She has a difficult personality," Ms Mormina replied. "Anyone who has worked with her knows that. I don't like people who don't behave correctly."

When Ms Mormina was asked whether she and Mr Benatti were hostile to WPP, she replied: "Who would not be?". But she said she had no personal hostility to Sir Martin, whom she did not know.

Ms Mormina said she was however pursuing a wrongful dismissal claim against WPP in the Milan labour court over her departure from the company.

Sir Martin says Benatti and Tinelli masterminded a series of blogs that defamed him by likening him to a mafia don who indulged in fraud, deception and money laundering.

The WPP boss and Ms Weber also claim the two men were responsible for distributing a "grossly offensive" image of them that they say breached their privacy.

Mr Browne asked Ms Mormina if her view that Ms Weber exploited her relationship with Sir Martin was shared by others at WPP Italy.

"It was a perception shared by people in our group," she replied. "The people I talked with shared it with me."

Ms Mormina said that Ms Weber's behaviour in the office changed in the second half of 2005.

Before that time, Mr Benatti had "controlled her exuberance", Ms Mormina said.

"After two maternity leaves, when I went back to work in 2005, my perception was that Mr Benatti was not able to handle or manage Ms Weber any more."

She said on one occasion in October 2005 Ms Weber would not accompany Mr Benatti to London for a meeting with Sir Martin.

By this time, the relationship between Sir Martin and Ms Weber was "no longer on", Mr Browne said.

In her witness statement, Ms Mormina said Ms Weber had been "challenging to work for".

"I felt she had a somewhat aggressive attitude and liked to exercise power. She was well known in the office for these traits."

Ms Mormina said that she learned of Ms Weber and Sir Martin's relationship on her second day at WPP after joining in February 2005.

The information was "widely known" at the time both in the office and the outside it among Milan's advertising industry.

"To expect people not to talk about a relationship between Daniela Weber, who was not particularly liked in the office, and one of the most powerful men in international media, is completely unrealistic. The impression people gave me was 'everybody knows'."

She said in her view Sir Martin and Ms Weber had not "taken steps" to keep their relationship private.

"It was generally known that they met publicly and holidayed together," she said. "I recall Daniela Weber took no steps to create the impression that she was holidaying elsewhere. My judgment was that she felt her position in the office was strengthened by her relationship with Martin Sorrell."

The case continues.

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