At the outbreak of World War I, he joined the Royal Flying Corps and worked as an assistant to David Henderson and Hugh Trenchard in France. Throughout the war, he wrote with Lady Juliet Duff, the widow of Sir Robin Duff, 2nd Baronet of Vaynol, who was killed on October 16, 1914, near Oostnieuwekirke while fighting in the 2nd Life Guards. The letters were ultimately published under the title Dear Animated Bust: Letters to Lady Juliet Duff. Richardson was born in Abingdon in 1873, as the third of four daughters. After the fourth daughter was born, Dorothy's father (Charles) began referring to her as his son. Richardson, meantime, "also attributed this habit to her own boylike willfulness". She lived at 'Whitefield', a huge mansion-style residence on Albert Park erected by her father in 1871 and currently owned by Abingdon School. Her family relocated to Worthing, West Sussex, in 1880, and then to Putney, London, in 1883. During her time in London, she "attended a progressive school influenced by the ideas of John Ruskin", in which "the pupils were encouraged to think for themselves". in which she "studied French, German, literature, logic and psychology".