Lord John Russell (1792-1878) was twice Prime Minister of Britain, once from 1846 to 1851, when he was notoriously unresponsive to the Great Irish Famine, and again briefly from 1865 to 1866. Between these premierships he served as Leader of the House and as Foreign Secretary; both of his terms as Prime Minister were brought to an end by disunity within his own party, the Whigs.
The position of Leader of the House of Commons is often held in conjunction to that of Prime Minister, although in Russell's case he performed both roles separately. Whereas the British Prime Minister is the de facto leader of the country, the Leader of the House of Commons is an administrative role responsible for the organisation of govermental business in the House.
Lord John Russell was the grandfather of the philosopher Bertrand Russell.