In 1990, she became Chairman of the Geffrye Museum, the museum of “historical English interiors” in east London, then an unconfident institution under the control of the Inner London Education Authority, which was itself on its last legs. With her usual shrewd assessment of character, she spotted just the right team of trustees and directors to galvanise the museum. She restored its pride and raised £5.3m to extend its premises. She was created a life peer in 1990, taking the Tory whip because that was the way to get on to the most interesting committees, but she was a crossbencher at heart, an independent spirit who sometimes refused on principle to vote with her party.Of her wide range of achievements in this period, a few stand out. When the wealthy and famous were pleading with the High Mistress and her very high cat, Oedipus, to secure places for their daughters, Brigstocke was innovative in creating bursary funds for those less privileged, even quietly financing a few girls from her own bank account. To both staff and students she was a great support, the perfect role model. She showed that it is possible to combine an important career with family life, and inspired them to achieve more than they ever thought possible.When she retired from St Paul’s in 1989, she directed her formidable energies to her next career, that of consummate committee chairman.

Many less dedicated educationalists would have faltered, but Brigstocke’s courage and steely resolve saw her through the crisis.She fostered the school’s reputation for academic rigour, making Latin and Physics parts of the core curriculum. But she also proved that glamour, style and a sense of fun are not incompatible with scholarship. She told jokes against herself with great relish and appeared on stage with the likes of John Cleese, dancing the can-can in a red net petticoat at a school fund-raising gala. She established international links and brought in distinguished outside speakers.With a shrewd perception of the cold winds that were blowing through the independent sector, her preferred commentaries on education came from The Economist, rather than the TES. Personal tragedy, Geoffrey’s death in the Turkish DC10 crash over Paris in 1974, coincided with her appointment to one of the pinnacles of the teaching profession, the post of High Mistress of St Paul’s Girls’ School.

“That keeps the audience’s attention focused.” She became an impressive speaker, with a mellifluous voice and a relaxed manner – and she never forgot the lipstick.On her return to the UK in 1965, she was appointed Headmistress of Francis Holland School, Clarence Gate, in London, where she seized a rather old-fashioned establishment by the collar and shook it into prominence as one of the best small schools in England. There she taught Latin at the National Cathedral School and made some of her most important contacts. She made her first public speech in the White House – a vote of thanks to the Kennedys for hosting a children’s tea party “Just wear plenty of lipstick,” she was advised. Although she soon switched to teaching, her hands-on experience of the retail trade was invaluable when she became an associate director of Great Universal Stores and Burberrys in 1993.There was a particularly busy period in her early life, when she taught Classics in London, produced her first three children, then escaped the humdrum to accompany her diplomat husband, Geoffrey Brigstocke, whom she married in 1952, to Washington.