Ms Boyle, known as Lady Saunders, was best known for presenting the music spectacular in the 1960s and 1970s.
The Italian-born British star’s career started as a model, before working as a continuity announcer for the BBC in the 1950s.
She was married to the late producer of The Mousetrap Sir Peter Saunders.
Lady Saunders went on to dip her toe into many other areas of the entertainment industry and had a career spanning more than six decades.
In her capacity as a host she fronted shows such as the Ivor Novello Awards and she had a long-running radio programme called Katie and Friends on BBC Radio 2.
She appeared on panel game shows and programmes including What’s My Line? and Juke Box Jury.
Lady Saunders was also known as an agony aunt for TV Times Magazine and for writing a weekly column on fashion and beauty in Sunday Graphic.
A lover of dogs, she was a committee member of Battersea Dogs Home for more than 25 years and wrote Battersea Tales – stories of rescues from the dogs home in 1997.
Born in Italy in 1926, the former Vogue model came to prominence in the 1950s when panel games were the hit of the nation’s one and only channel.
Her English rose beauty, despite her Italian heritage, plus her charm and cut-glass accent were the perfect combination for the BBC at the time.
When the Eurovision song contest began to grab audience attention, she seemed the obvious choice to host it, famed for her poise, unflappability and perfect French.
It was her highest calibre role, which she performed four times across 13 years when the event was held in the UK - most notably in 1974 in Brighton when a little known Swedish foursome who went by the name of Abba triumphed.
She married three times and wrote about her life in showbiz in 1980 in autobiography What This Katie Did.
In 1998, she said: “My whole career really started by accident. There was a time when I was on the BBC three times a week - it seems very strange to think of that now, but it was the only thing people watched.”