Nan Bullock was baptised Margaret Annie and known generally as Annie when she was younger but came to be known as Nan later. She was born in 1886 in Peking [now Beijing], the only daughter of Thomas Lowndes Bullock, HBM Consul in China till 1897 and Professor of Chinese at Oxford 1899-1915, and Florence Louisa Elizabeth Horton. She was educated at Oxford High School and came to Girton College in 1904 as a Barbara Leigh Smith Bodichon Scholar to study mathematics. She took Part I of the Tripos in 1907. She undertook work at the National Service (Recruiting Office) in Oxford 1916-18, and evening and Sunday work at the Red Cross Auxiliary Hospital, also 1916-18. She was awarded the MBE in January 1919. In 1920, Nan married Sir Claud Severn. She lived for many years at Wallingford in Berkshire. She died in 1967.