Bernard Hailstone, left, as part of London’s Auxiliary Fire Service in c.1940 

While he was with them, 7th Light Cavalry were in daily contact with the enemy. Hailstone painted the portrait in the evenings, my father sitting, he recalled, on a crate at the rear of his Stuart tank. The 26-year-old man in the picture, tense, lean, dangerous, is in many ways so different from the jovial convivial father that I knew, though I could always see it was him. For me, the image conjures the gulf between war and peace.

Louis's friend Ian Aitken wrote in his Guardian obituary: "The portrait shows a young man in a squashy black beret who could easily be mistaken for an Italian condottiere painted by a Renaissance master. Sweaty, self-confident and fierce, it is the face of a real soldier."

After the war, Hailstone showed the painting at the Royal Academy's 1946 summer exhibition, where it was described as "Portrait sketch". It is not as finished as one of Hailstone's official war portraits, many of which can be seen in the Imperial War Museum. The sketchy quality adds to the feeling of immediacy. Later he sold or gave it to my father, and the two remained in distant contact.

While Louis embarked on an adventurous career of foreign corresponding, Bernard Hailstone began to develop a successful portrait practice. Always retaining bohemian attributes, he painted many of Britain's great and good, from the Queen to Churchill. With such subjects he did not play about-the last portrait of Churchill, now in the Imperial War Museum, is powerful and utterly correct in all its details. But he was never overawed, and when, as with Lord Mountbatten, he detected a certain phoniness, it was there in his portrayal.

Twenty years after that Burmese encounter, we were living in Washington D.C. when Hailstone came to stay with us. He was expecting a commission to paint Paul Mellon, the billionaire art collector. My parents put him up in our spare bedroom. Mellon's private secretary proved elusive, and the expected week's sojourn stretched to a month or more. Hailstone, who seems to have been short of funds, offered to paint my mother Patricia in lieu of rent.