She was an acknowledged authority on land tenure and reform in Iran (including Saljuq, Mongol, Safavid and Qajar administration and institutions, and local and tribal histories).

[3] From 1939 to 1945, Lambton was Press attaché of the British Legation to Tehran, and then Professor of Persian at SOAS from 1953 to 1979, succeeding Arthur Arberry as holder of that chair.

After the decision to nationalize Iran's oil interests in 1951, she advised the British government to undermine the authority of Mossadegh's regime.

[4][5] As Professor Emeritus of the Diocese of Newcastle and Chairman of the Iran Diocesan Association, Lambton served on the Middle East Committee and advised Archbishops on inter-faith matters.

She was later awarded the Cross of St Augustine in 2004 by the Archbishop of Canterbury in acknowledgement of her work and commitment to Christianity and the Church of England.