Headlam-Morley was born on 10 December 1902 in Cambridge, Cambridgeshire, England,[1] the only daughter of James Wycliffe Headlam, an academic and civil servant who was involved in drafting the Treaty of Versailles, and Else (née Sonntag), a musician and composer who was born and brought up in Germany.
[3] She studied modern history at Somerville College, Oxford, graduating with a second class Bachelor of Arts (BA) degree in 1924.
[1] She then undertook research in modern European political history, and completed a Bachelor of Letters (BLitt) degree in 1926.
[6] She belonged to the traditional school of international relations in which the subject was considered a subfield of history and not a social science.
[3] She was a member of the Conservative Party, and stood as a candidate in the 1936 election to Durham County Council.