The letter, which is due to go up for auction on 27 February, also refers to primroses the late queen had picked, which she asked to be shared among staff at Royal Lodge.
The letter was one of several found addressed to Beatrice Stillman, the former head housemaid at Royal Lodge.
Another, from Princess Margaret, asked Stillman to “look after my bathing suit”.
When Stillman’s brother-in-law John Dicker was killed in an air raid in 1940, the Queen Mother invited his widow, Stillman’s sister, and their two young daughters, Rene and Jean, to play with the princesses at Royal Lodge.
