Lady Falkender, Harold Wilson’s former right-hand woman, died of pneumonia 10 days ago, aged 86, but the news emerged only late on Friday, triggering a flurry of tributes from politicians and commentators.

It brought down the curtain on a life that had been the subject of intrigue and lawsuits, but which also blazed a trail for women in politics.

Formerly Marcia Williams, Falkender was the private and political secretary to the Labour prime minister during his premiership in the 1960s and 1970s.

The position made her the most powerful woman in No 10 until Margaret Thatcher became prime minister. But she really came to prominence – and controversy – after Wilson’s sudden resignation in 1976, although she continued to handle his private affairs until his death in 1995.

It was claimed that Falkender drafted the former prime minister’s controversial list of resignation honours, which became known as “the lavender list” because it was written on lavender-coloured paper.

But in 2007, she won £75,000 in libel damages from the BBC over her portrayal in a drama repeating the claim and suggesting that she had included the names of people who had assisted her personally or from whom she hoped to receive assistance personally. It also wrongly suggested that she had had a brief, adulterous affair with Wilson and had subsequently used this to blackmail him.

Wilson believed many of the allegations made against him and Williams were the work of a smear campaign by MI5. But these did not prevent her from being elevated to the Lords in 1974, although she did not speak in the chamber despite attending for 40 years.

“My peerage has been a great problem to me because I have never known how to handle it,” she said. “But now I know myself pretty well. And I think if the press has got me wrong there is nothing I can do to put it right.”

She had two sons during her relationship with Walter Terry, one-time political editor of the Daily Mail, and had a five-year marriage to George Williams. She also worked as a Mail columnist and wrote two books about her time in Downing Street.

Her loyalty to Wilson was unswerving and she gave short shrift to his enemies, including Roy Hattersley, who was an ally of Roy Jenkins, a thorn in Wilson’s side. “She was a very able woman, and I think Harold Wilson was very lucky to have her by his side for 40 years,” said Lord Hattersley, who served as a minister under Wilson. “I have no idea what the real relationship with Harold Wilson was, but politically she was a thoroughly good thing.”

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Lord Lipsey, who worked as a political adviser in Wilson’s government, said the ultimate source of her power lay in her relationship with Wilson.

“She didn’t have tremendous influence over policy matters, but she had a general influence over Harold and she was his confidante – the person to whom he could turn when things were getting tough and get a comforting reply, and perhaps he found common sense on occasion.”

Asked if Wilson was scared of her, Lipsey told BBC Radio 4’s Today programme: “We’ll never know. She was a formidable personality.” Even her death was something of an enigma.