Sarah Foot: Author, journalist, social worker and family matriarch acclaimed for her chronicles of 'disappearing Cornwall'

"The secret of Sarah's success was that she caught the spirit of place and people's personalities so perfectly, " said her publisher, Michael Williams

Foot in London when she was working for the 'Evening Standard': George Best and Cliff Richard were among those she interviewed

Sarah Foot was a journalist, author, social worker and matriarch of the Foot clan. She was the niece of the former Labour leader Michael Foot, daughter of the diplomat and politician Lord Caradon and sister of the investigative journalist Paul Foot, and despite spending much of her life caring for her family she wrote a string of evocative books on Cornwall which recreated a disappearing way of life.

Foot was best-known for her intimate family memoir My Grandfather, Isaac Foot, about the Devon builder's son who left school at 14 but through his drive and love of learning become a crusading lawyer, Methodist preacher, Liberal MP and scholar, amassing one of the largest private libraries in England – more than 70,000 books. His seven children inherited his intelligence and radical views and the influential dynasty included Michael, the Labour Solicitor-General Sir Dingle Foot, the Liberal politician John (later Lord) Foot and Sarah's father Hugh, who became Governor of Cyprus and Jamaica. Sarah's two younger brothers were Oliver Foot, the philanthropist who founded the Orbis eye charity, and Ben, Director of Save the Children in Nigeria.

Sarah and her two eldest brothers spent part of their childhood in Jamaica and formed lifelong ties with the country and its people, often escaping the formality of diplomatic life at Government House in Kingston to play with the children of the black maids and drivers. At the age of eight the horse-mad Sarah (and her pony) began boarding at Hanford, an idyllic Dorset prep school, and enjoyed holidays with her extended family at her grandfather's home, Pencrebar, near Callington in Cornwall.

Her father became the last governor of Cyprus, overseeing the move to independence, and as a vivacious teenager Foot and her stylish half-Italian mother Sylvia set the pace among the island's social set. After two years in Italy she rejected the traditional debutante season in London to become a journalist on the London Evening Standard, interviewing celebrities including Cliff Richard and George Best.

A glamorous young socialite, famous for her warmth, she featured regularly in Harper's Bazaar and sat for the society photographer Tom Hustler. At 21 she married her father's aide-de-camp, Timothy Winter Burbury, a dashing young officer in the Blues and Royals and for two years she worked for the Africa Bureau charity before postings to Aden and Germany and the arrival of their two children, Camilla and Charles.

Traumatised by his experiences during the Troubles in Northern Ireland, Timothy took early retirement and for years afterwards slept with a gun under his pillow, often waking up screaming, convinced he was still fighting for his life. The family moved to a cottage near St Mellion in Cornwall where, despite a chronic lack of funds, they were swamped with invitations to every party.

Foot became women's editor of the Western Morning News and interviewed characters who represented the last vestiges of "vanishing Cornwall", like Joe Halls, who at 80 still farmed on Bodmin Moor in an ancient slate-faced farmhouse without electricity, cutting his own peat and rounding up his sheep on horseback. She recalled Joe's description of Methodist Sunday School picnics at the reputedly bottomless Dozmary Pool where Sir Bedivere is said to have flung King Arthur's sword, Excalibur. "Us children went in a boat on Dozmary," he said, "then back at the chapel the organ would be brought outside to an arena just below and everyone would sing the Wesleyan hymns."

This evocation of a simpler era infused Foot's first book, the best-selling Following the River Fowey for the Cornish publishers Bosinney Books in 1979. She relished tracing the river's source on the slopes of Brown Willy on Bodmin Moor while filming a Westward TV feature. "It was a perfect May morning of wild flowers and dragonflies" she recalled, "and we found the trickle that was the infant Fowey. It was one of the great days of my life." As her publisher, Michael Williams, observed, "The secret of Sarah's success was that she caught the spirit of place and people's personalities so perfectly."

In 1988 she started a social work degree but thanks to her warmth and humanity was head-hunted to work at Derriford Hospital neurology department and St Luke's Hospice in Plymouth. "Wherever she went, everyone adored her," her daughter Camilla remembered, "because she made you feel you were adored."

Foot was proud that her son Charlie, an expert deep sea diver, continued the family links with Jamaica, helping to clear Kingston harbour of hurricane debris and farming coffee with his uncle Oliver in the Blue Mountains. He married a Jamaican woman and built three guest cottages, providing employment for many local people

In 1991 Camilla's daughter Hannah was born with the life-threatening cranio-facial condition Pfeiffer Syndrome, and Foot cared for her eldest grandson while Camilla spent months at Hannah's bedside as she underwent more than 120 operations. Hannah lived a fulfilling life, and when she died last November at the age of 23 she had survived longer than anyone with this complex syndrome.

By now Foot was suffering from Alzheimer's but she remained gracious and welcoming to the last, and the day before she died, danced ecstatically to a Bob Marley track and enjoyed the rich lilt of her Jamaican daughter-in-law's conversation. Staff at her care home nicknamed her "the social butterfly" because of her legions of visitors. She died from complications of Alzheimer's.

Sarah Dingle Foot, writer and social worker: born Bath 24 September 1939; married Timothy Burbury (died 2013; one daughter, one son); died Saltash, Cornwall 28 February 2015.