 He returned to Tehran in 1872 as assistant to Grand Vizier Mirza Hosein Khan Moshir od-Dowleh, and became the chief of the Persian legation in London (and later ambassador) in 1872.He remained in the position until 1888, and lost his position in 1889 as the result of a scandal over selling a cancelled concession for a lottery.Nasereddin Shah explains in his third trip's memoir, how he went to Mirza Melkum Khan's house an evening, met his wife and his three daughters two of them as old as 19-20 and the third one who was 6 at the time (1889).