Both Elizabeth and Philip shared their happiness in letters written from Birkhall, excerpted in William Shawcross's Counting One's Blessings: The Selected Letters of Queen Elizabeth the Queen Mother. Elizabeth wrote to her mother, "It's so lovely and peaceful just now — Philip is reading full length on the sofa, Susan is stretched out by the fire, Rummy [presumably their new dog] is fast asleep in his box beside the fire. . . It's heaven up here!"
Philip wrote an unusually sentimental note to his new mother-in-law about "Lilibet," the family's nickname for Elizabeth. He wrote, "Lilibet is the only 'thing' in this world which is absolutely real to me. . . Cherish Lilibet? I wonder if that word is enough to express what is in me."
(The couple returned to Birkhall in 1972 to take their 25th anniversary portrait!)