Linda, far right, with her family who lived in New York
His bride, Linda Eastman, went on to build her own reputation as a photographer, musician and businesswoman. Their relationship remained strong to the end of her life.
Sir Paul's spokesman said: "The coming days are going to be very difficult for Paul. People may not realise, with the exception of one occasion, Paul and Linda never spent a night apart in the 30 years that they have loved each other."
Photographer of the stars
Lady Linda, as she would later become, was born in 1942 in New York, USA. Her father was a successful lawyer and Linda was educated at the prestigious Scarsdale High School.
After leaving school, she became a photographer and captured some of the most illustrious rock stars of the 1960s, including the Rolling Stones, the Who and Jimi Hendrix. She put on more than 70 exhibitions of her work and produced five best-selling books of her photography.
On a trip to London in 1967 she photographed the Beatles, fell in love with Paul McCartney, the bassist, singer and co-writer of the majority of the band's songs. She married him two years later.
A vegetarian long before it became fashionable
Linda McCartney introduced her husband and many Britons to vegetarianism. She said she did not eat anything with a face.
After the Beatles split up in 1970, Paul McCartney brought her into his new band, Wings, where she sang and played keyboards.
Critics at the time derided her involvement as a form of nepotism but the group's back-catalogue continues to contribute to the position of Sir Paul McCartney as one of Britain's richest people.
Lady Linda's vegetarianism provided her with business success. Her own range of food products, marketed in the 1990s, made her a millionaire in her own right.
Tireless campaigner for animals
The hostility against her from some sections of the public and media continued. Both Sir Paul and Lady Linda were fined for possessing cannabis in 1972 and admitted having the drug again in 1984.
But Lady Linda refused to let the attacks deter her from publicly supporting the causes she believed in. She worked tirelessly on behalf of the anti-fur group Lynx, Greenpeace, the Council for the Protection of Rural England, Friends of the Earth, People for the Ethical Treatment of Animals, the Hammersmith Cancer Hospital, War Child and the League Against Cruel Sports
League Chairman John Cooper said: "Linda was an avid campaigner for the League Against Cruel Sports.
"She worked tirelessly on behalf of hunted animals, sometimes in a very public capacity, sometimes very quietly behind the scenes.
"Her tragic death will leave a feeling of great sadness with all those who oppose hunting."
Mother of a talented family
The McCartneys had three children, Mary, Stella and James. Linda also had a daughter Heather from a previous marriage.
Stella McCartney has achieved fame in her own right as a fashion designer and more recently a member of the UK Government's 2000 committee, which is seeking to promote Britain around the world.
Lady Linda's final public appearance was last month sitting in the front row of her daughter's fashion show when Stella unveiled her latest designs for Chloe in Paris.
She cheered as models walked down the catwalk and jumped up to join the standing ovation.