The estranged family of Lady Lucan, whose husband famously vanished more than four decades ago, have said they will remember her "lovingly and with admiration".
The 80-year-old was found dead at her home in Westminster, central London, by police on Tuesday afternoon after she was reported missing.
She was one of the last people to see her husband, John Bingham, the 7th Earl of Lucan, alive before he disappeared in November 1974.
He vanished after the body of the family's nanny was found at their home in Belgravia.
The family of Lady Lucan, formally named Veronica, Dowager Countess of Lucan, said in a statement: "Veronica's children and her sisters are deeply saddened by the news and circumstances of her death.
"Although Veronica severed relations with her family in the 1980s, and continued to decline contact with them right up until her death, all of them remember her lovingly and with admiration.
"She had a sharp mind, and when she spoke it, she did so eloquently. She was courageous and, at times, outrageous, with a mischievous sense of humour.
"She was, in her day, beautiful and throughout her life fragile and vulnerable, struggling as she did with mental infirmity.
"To us she was and is unforgettable."
Lady Lucan was found unresponsive when police forced entry to her home amid concerns for her welfare.
Her son, George Bingham, the 8th Earl Lucan, told the Daily Mail: "She passed away yesterday at home, alone and apparently peacefully.
"Police were alerted by a companion to a three-day absence and made entry today."
A Metropolitan Police spokesman said: "Police attended an address on Eaton Row in Westminster ... following concerns for the welfare of an elderly occupant.
"Officers forced entry and found an 80-year-old woman unresponsive.
"Police and London Ambulance Service attended. Although we await formal identification we are confident that the deceased is Lady Lucan."
The death is being treated as unexplained but is not believed to be suspicious, police said.
Lord Lucan vanished following the discovery of the body of nanny Sandra Rivett at the family's home at 46 Lower Belgrave Street, central London, on November 7 1974.
Although officially declared dead by the High Court in 1999, he was reportedly sighted in Australia, Ireland, South Africa and New Zealand, and claims even surfaced that he had fled to India and lived as a hippy called "Jungly Barry".
On the night of his disappearance, Lady Lucan was also beaten severely before she managed to escape and raise the alarm at a nearby pub, the Plumbers Arms.
Roger Bray, who wrote one of the first newspaper reports about the mystery, heard how Lady Lucan "staggered" into the bar "covered in blood".
Derrick Whitehouse, head barman at the Plumbers Arms, told the journalist she had said: "I think my neck has been broken. He tried to strangle me."
Mr Whitehouse added: "She just said: 'I'm dying'. She kept going on about the children. 'My children, my children', she said."
Lord Lucan's car was later found abandoned and soaked in blood in Newhaven, East Sussex, and a year later an inquest jury declared the wealthy peer was the killer.
Earlier this year, Lady Lucan gave a television interview in which she said she believed Lord Lucan had made the "brave" decision to take his own life.
Ahead of the hour-long documentary interview called Lord Lucan: My Husband, The Truth, Radio Times magazine shared some of her words with director Michael Waldman.
She said: "I would say he got on the ferry and jumped off in the middle of the Channel in the way of the propellers so that his remains wouldn't be found - I think quite brave."
She also spoke about her depression and her husband's violent nature following their marriage in 1963.
Describing how he would beat her with a cane to get the "mad ideas out of your head", she said: "He could have hit harder. They were measured blows.
"He must have got pleasure out of it because he had intercourse (with me) afterwards."