Leyser began studying at St Paul's School in London in 1937, with the medieval historian Wilhelm Levison, a relative of Otto's, helping with the fees.
[3] In 1939 he won a demyship to study at Magdalen College, Oxford, but joined the Army a year later after a short spell in an internment camp on the Isle of Man as an enemy alien.
Leyser continued his military service after the Second World War, serving as a captain and later a major in the Territorial and Army Volunteer Reserve.
He was elected a Fellow of the British Academy in 1983 and a year later was appointed Chichele Professor of Medieval History at All Souls College.
[3] They had four children together: Conrad, an Oxford medievalist; Ottoline, a Cambridge plant biologist; Crispin, a television consultant; and Matilda, a circus performer and author.