He served as
British Ambassador to
Vienna ending in 1841. He was invested as a
Knight Grand Cross of the
Order of the Bath and admitted to the
Privy Council in 1822. In 1839 he was raised to the peerage as
Baron Beauvale, of
Beauvale in the County of Nottingham. In 1848 he succeeded his elder brother as third
Viscount Melbourne. Despite a certain personal distance between them,
Lord Palmerston, as
Foreign Secretary placed great confidence in Lamb, wrote to him in a courteous style very different from his usual brusque manner, and left the running of the Vienna Embassy almost entirely in his hands. The coolness was due to Palmerston's decades-long affair with Lamb's sister Emily, Lady Cowper; Lamb disapproved of the affair and disapproved equally of their eventual marriage, although this proved to be very happy. Palmerston's biographer notes that the marriage coincided with the early stages of the
Oriental Crisis of 1840, and that the two men, although they were then personally barely on speaking terms, co-operated in an entirely professional way to resolve it. Palmerston, in addition to his real respect for Lamb, was anxious not to quarrel with him for Emily's sake: as
Charles Greville remarked: "the Chief (Palmerston) is devoted to the sister and the sister to the brother". Relations between the two men became friendlier in later years, partly because both Palmerston and Emily were fond of Frederick's wife Alexandrina. ==Personal life==