William Lamb (15 March 1779 – 24 November 1848) was Home Secretary (1830–1834) and Prime Minister (1834 and 1835–1841). He was educated at Eton and Trinity College, Cambridge, and became associated with Percy Bysshe Shelley and Lord Byron. In 1805 he inherited his father's title and married Lady Caroline Ponsonby. The next year he was elected to the British House of Commons as the Whig MP for Leominster. His wife had a public affair with Lord Byron – she coined the famous description of the poet as 'mad, bad, and dangerous to know'. Melbourne was Prime Minister when Queen Victoria came to the throne in 1837 and became her advisor and mentor. In May 1839, Melbourne's resignation led to the Bedchamber Crisis when Robert Peel, the prospective Prime Minister, asked the Queen to dismiss some of the relatives of Whig MPs in her entourage. The Queen refused so Peel declined to form a new government. Melbourne was eventually persuaded to stay on as Prime Minister. The second largest city in Australia, Melbourne, was named in his honour.

Inscribed on the back with the names of the artist and sitter and the date, 1844.