Early in 1945, Tippett's closest woman-friend, Francesca Allinson, then 43 years old, took her own life - partly for personal reasons, partly out of a deep sense of grief for what had happened in the war. It was some time, indeed five years, before Tippett felt he could produce some kind of musical commemoration. He eventually decided to write a song-cycle using verses by two young poets, Alun Lewis (1915-1944) and Sidney Keyes(1922-1943,who had both been killed in the war.

Urged on by Peter Pears, who commissioned it, he took time off from writing Act I of his opera, The Midsummer Marriage, and finished the first two songs. But an attack of hepatitis forced him to delay completion of the cycle until he had finished the opera's second Act in 1951/ By that time, also, he felt that his personal emotions had been transmuted into more generalised feelings: thus, later, he declared the underlying theme of the cycle to be 'Love under the shadow of death.' The first performnace of The Heart's Assurance was given by Pears and Britten at the Wigmore Hall, London in May 1951. A version with chamber orchestra accompaniment was subsequently prepared by Meirion Bowen and premiered in 1985.