In the summer of 1982, while Lebanon was under Israeli attack as it is now, Pamela Cooper worked tirelessly helping wounded and starved children in Beirut. Two months into the siege, she and other foreign women marched to the Israeli lines and demanded a ceasefire. "We women are witnesses to the destruction of Beirut and the killing of civilians," she said through a loudhailer:

We can attest to the fact that there is an unbearable shortage of food, water, fuel, medicines and electricity . . . We foreign medical workers in West Beirut are witnesses to the maiming and death of a large number of civilian casualties from the Israeli use of weapons, such as cluster bombs and phosphorous bombs, and the shelling of hospitals.

History does not relate what the Israeli soldiers made of Mrs Cooper. She was about to turn 72. If Pam Cooper had not died on 13 July, she and her husband Derek would have wanted to return to Beirut to do their best for the latest victims.

Nothing in her upbringing, apart from an inherited and profound belief in right and wrong, determined the course of her life. From a conventionally mixed upper-upper-middle-class background of Edwardian England, she chose a life that challenged convention.

Of her birth in 1910 in Chelsea, London, she wrote in her memoirs, A Cloud of Forgetting (1993), "I arrived by mistake, the outcome, I was told, of the 'safe period', 11 months after my brother Michael's birth." Her parents were the Rev Arthur H. Fletcher, whose father and three brothers were also Church of Ireland clergymen from County Waterford, and his wife Alice Hodgson. At Grandmother Hodgson's house in Cadogan Square, the baby Pamela used to ride a Great Dane to the children's rooms at the top of the house.

She remembered the day the First World War began, of spitting on the Kaiser's picture in the Illustrated London News and of her father's departure as chaplain to the British forces in France. By her teens, she was a society beauty. She met and fell in love with the dashing, but equally penurious, Patrick Hore-Ruthven. Hore-Ruthven's father would in 1945 earn back the ancient Scots title of Earl of Gowrie, abolished by James VI of Scotland after the famous "Gowrie conspiracy", through his service as Governor-General of Australia. "When I first met Pat,"she wrote, "he had been temporarily rusticated from Cambridge for biting a policeman on the nose." He joined his grandfather's old regiment, the Rifle Brigade, and served for three years in Malta.

Her choice of church for their wedding, on 4 January 1939, was typically perverse: "I insisted that, if I must be married in London, it had to be Westminster Abbey. This was because I disliked organs and knew the choir would sing unaccompanied."

The first of their two sons, Greysteil, was born soon after the Second World War began. Pam followed Pat to Cairo, where he left his grandfather's old regiment to join the new SAS. Among her friends in Cairo were the travel writer Freya Stark and Jacqueline Lampson, young wife of the British ambassador. When Pam Hore-Ruthven conceived her second son, Malise, she embarked on a hazardous journey dodging U-boats in the Atlantic to give birth in Ireland. Pat died from wounds in a raid on the Italians in the Western Desert at Christmas 1942.

Her father-in-law was serving as Deputy Governor of Windsor Castle, and Pam Hore-Ruthven came to live there as a lady-in-waiting to Queen Elizabeth, with her two young sons. While there, she met the second love of her life, another war hero, Major Derek Cooper of the Life Guards. Cooper had served in France and Belgium, where he won the Military Cross. He had also served in Palestine, where he felt strongly the British betrayal of the Palestinian Arabs who had been driven out in 1948.

His status as a divorced man put Pam into conflict with King George VI's uncle by marriage the Earl of Athlone and his wife, Princess Alice. Not only did Princess Alice disapprove of Pam's marriage to a divorced man, but her husband was colonel of Derek's regiment. Pam moved out of Windsor Castle and Derek resigned his commission. They married in 1952 and moved to Dunlewy in County Donegal, where they lived until 1974.

Both loved skiing and the Donegal "season" surrounding the American art-collector Henry McIlhenny and the painter Derek Hill. But their real passion was bringing help to victims of war, disaster and revolution. It began with Save the Children during the Hungarian revolution of 1956, when they went to the border at Andau and spent months rescuing refugees. It continued through the massive Iranian earthquake of 1962 and took them back again and again to the Middle East to help the Palestinians.

Michael Adams, the Guardian Middle East correspondent who founded the magazine Middle East International to redress the anti-Palestinian bias in the British press, introduced me to the Coopers in 1976. Our first meeting was a revelation that began my love affair with the best of Anglo-Ireland. Their unlikely collection of friends and hangers-on at their house in Ebury Mews incarnated all I had read in Evelyn Waugh and Wilfred Thesiger. Pam Cooper was deliciously glamorous, and Major Derek Cooper sported a dramatic moustache of a kind that I had seen only in Second World War films. His soft voice betrayed a gentleness of character that contrasted with Pam's greater determination and ferocity. (I never understood, apart from those vast blue eyes, why her family called her Frog.)

Although 40 years my senior, the Coopers seemed like contemporaries. I realised the difference in generations only once, when my wife and I had Pam and Derek to dinner at our new house in Notting Hill. After inspecting most of the nine bedrooms and the communal garden, Pam said, "It's a lovely house, Charlie, but won't you miss London?"

When I shaved my beard in 1983, Pam was the only woman I knew who objected. To her, I no longer resembled a Palestinian freedom fighter. When I was in hospital, she walked all the way from Ebury Mews to Harley Street, aged 74, to visit me. She had a strong, if original, faith that had its origins in her religious upbringing. Tied to it was a generosity that was almost selfless.

Pam and Derek Cooper moved to a house for retired gentlefolk in Wiltshire, but it was not to retire. Whenever we went to visit, we had to search for Derek - usually discovering him in the woods, happily clearing a way with a kind of machete, or in the river fishing for trout. When Pam's eyesight began to go in her early nineties, Derek would read to her. She never lost her ironic and cutting humour, any more than she did her outrage that the Palestinians were still treated so cruelly.

Her elder son, Grey, succeeded in 1955 as the second Earl of Gowrie and became a minister in Margaret Thatcher's government and the younger, Malise, is the author of many books on her beloved Middle East.

Pamela Margaret Fletcher, courtier and campaigner: born London 24 October 1910; Extra Woman of the Bedchamber to Queen Elizabeth 1948-51; married 1939 Patrick Hore-Ruthven (died 1942, his widow styled 1945-52 Viscountess Ruthven of Canberra; two sons), 1952 Major Derek Cooper; died Amesbury, Wiltshire 13 July 2006.