Lady Katherine Brandram was a naturalised British citizen, a shy, sweet-natured widow, who had lived in a small house with a garden at Marlow for the past 60 years. Unassuming and bird-like in appearance, latterly cared for by a nurse, and visited often by her son and his family, she gave no hint of her extraordinary past. Yet she was the daughter of a king, the sister of three kings and a queen, the aunt of a king and two other queens and a first cousin of the Duke of Edinburgh.

She was born Princess Katherine of Greece and Denmark, the third and last surviving daughter of King Constantine I of Greece. Her three brothers, George II (born 23 years before her), Alexander I and Paul I were kings of Greece in succession, and one of her sisters was Queen Helen of Romania. She was the last surviving great-grand-daughter of Queen Victoria. (One great-grandson survives, aged 91, Count Carl Johann Bernadotte.)

Princess Katherine was a late addition to the Greek Royal Family and her birth, at the Royal Palace in Athens in May 1913, came at a traumatic time in the history of Greece, not long after the Balkan War, and just a few weeks after the assassination of her grandfather, King George I of Greece, in Salonika. Her mother, Queen Sophie, was a daughter of the Empress Frederick of Germany and a sister of the Kaiser. Relations between her parents were at a low ebb, and indeed, in 1912, her father had taken a mistress, Paula von Ostheim, sometimes known as Princess of Saxe-Weimar. Thus the birth of Princess Katherine caused some surprise in royal circles. At her christening, she became a god-daughter of all the men of the Greek Army and Navy.

Her early life was a mixture of being a royal princess and a virtual gypsy, as the Greek Royal Family went in and out of exile. During the First World War, Princess Katherine’s parents were accused of being pro-German, and relations between Britain and Greece were strained. Their lives were often in danger. Indeed, the young Princess Katherine had to be protected against the danger of kidnapping, while her early memories were of machinegun and rifle fire. In 1916 she was carried two miles in her mother’s arms from Tatoi, the residence of the Greek Royal Family, part of which had been burnt by the secret police. A year later, aged four, she accompanied her parents into exile in Switzerland.

King Constantine was King of Greece for a further two years between 1920 and 1922, before abdicating and going once more into exile. He left Athens on the night of September 30 and sailed to the Sicilian capital, Palermo. Queen Sophie, Princess Katherine and Prince Nicholas accompanied him. On January 11, 1923, Princess Katherine was one of the family who rushed to her father’s bedside when he fainted in the Hotel Villa Igiea and died without regaining consciousness.

Thereafter the family spent long years of exile in Florence, living at the Villa Sparta, where Princess Katherine became a keen painter. From her earliest childhood she had English governesses and went to school in Broadstairs and to North Foreland Lodge in England. Her mother died in January 1932, and thereafter she made her home with her sister Queen Helen, still at the Villa Sparta in Florence.

In 1934 she was a bridesmaid (with the present Queen) to her first cousin, Princess Marina, when she married the Duke of Kent in Westminster Abbey. In 1935 she made a round-the-world trip, visiting Hollywood as a tourist, but was forced to leave in haste when publicity men tried to make her accept a screen offer.

The monarchy was restored in Greece in November 1935, with her brother George II as King. The following year she and her sister, Irene, returned to Athens, where she undertook social and welfare work. The Greeks judged her “open, vivacious and unaffected”. At the outbreak of war in 1939 she joined the Greek Red Cross, working in an operating theatre, and becoming accustomed to caring for the war-wounded. She frequently nursed Air Force men she had known socially in peacetime. One particular Air Force officer, whom she nursed back to health, asked her to meet him for tea at the King George Hotel, but failed to appear. She was deeply distressed to learn that he had been killed that day in action.

In April 1941 Princess Katherine accompanied her brother, Crown Prince Paul, his wife, Frederika, their children and Princess Aspasia and her daughter Princess Alexandra of Greece, on their flight from Greece in a Sunderland flying boat. They went to Crete and Egypt, and finally she and Crown Princess Frederika and the children settled in exile in South Africa. For four years she was completely without news of her sister Queen Helen.

They made their home in a tiny five-room bungalow and cooked for themselves. Princess Katherine nursed for six months at the Wynberg Military Hospital in Cape Town, and then did voluntary war-work for two and a half years at the Tombani House, run by St Dunstan’s, where she cared for blinded casualties from the Western Desert. She worked under the name of Sister Katherine.

After the war she returned to Egypt and on sailing to London in Ascania in 1946 to join her brother, King George II, she met a Royal Artillery officer with a Military Cross, Major Richard Brandram, the son of a retired prep school master from Bickley, Kent. She was seasick on board, but met him again as they docked at Liverpool and they agreed to lunch together. Three weeks later they were secretly engaged. In February 1947 King George of Greece announced the engagement “with particular satisfaction”. The major’s mother was the victim of several press enquiries. She told them that the Princess sometimes helped her in the kitchen, and stated: “It isn’t every day you become the future mother-in-law of a princess”.

The wedding was set for April 1947, but King George II died of a sudden heart attack three weeks before. Princess Katherine was in the Palace when he was taken ill. Instead, his successor, King Paul, her second brother, was best man, wearing his customary monocle, and a mourning band. The ceremony, both Anglican and Greek Orthodox, took place in the private ballroom of the Palace. The Armed Services gave her a dowry of £10,000 and the gendarmes of Greece gave her a diamond bracelet and £4,000. Thereafter, the couple left for Baghdad, where she began the roving life of a British Army officer’s wife.

When they settled in England, King George VI granted the Princess the title of Lady Katherine Brandram with precedence as the daughter of a duke. This title she used in England. She was amused that she had to pay the College of Arms the fee of £25 to regularise the situation. Lady Katherine was a guest at the present Queen’s wedding in 1947.

Lady Katherine and Major Brandram lived first in Eaton Square, but later retired to Marlow. Dick Brandram died there after a difficult illness in 1994, aged 82. One of Lady Katherine’s last public appearances was at the wedding of Crown Prince Paul of Greece in the summer of 1995, which she attended in a wheelchair. She also attended the Duke of Edinburgh’s 80th birthday service in St George’s Chapel in June 2001, members of the congregation being surprised at how many members of the Royal Family paused to greet this tiny figure that they did not recognise.

Lady Katherine is survived by her son, Paul, born in 1948, and her three grandchildren.

Lady Katherine Brandram, formerly Princess Katherine of Greece and Denmark, was born on May 4, 1913. She died on October 2, 2007, aged 94