Baldwin succeeded Bonar Law in 1923. He soon called a General Election. But failed to gain a working majority. The prize of government went instead for the first time to Labour.

In the first-ever Labour government the survival of MacDonald's small Commons majority depended on the good will of opposition parties. This difficult situation prompted him to call an election. His Labour administration was then heavily defeated in the election.

MacDonald's Labour government lost the next election, and Baldwin was returned as Prime Minister in November 1924, holding his second premiership until 1929.

In his second minority government in 1929, MacDonald set an historic precedent by appointing Margaret Bondfield as the first female minister.

Economic crises, including the doubling of unemployment levels, persuaded him to include the opposition leaders in a cross-party National Government.

Baldwin was the de facto figurehead of the 1930s National Government, and properly regained the premiership after the 1935 election.

However, this step lost him the support of his own party and he resigned in 1935. The coalition was considered by many party members to be a cynical betrayal of their hopes. MacDonald subsequently lost his seat.

He encouraged the rise of Labour to divide the Liberals.

As he left Number 10 for the last time on 28 May 1937 he said: "I am a gentleman at large now."

Chamberlain famously met German chancellor Adolf Hitler in Munich 1938 the result of which was an agreement that Britain and Germany would never again go to war. "I believe," he declared on his return to the UK, "it is peace for our time." However, the success of 'appeasement' was shortlived, as Hitler occupied Prague the following year. The subsequent invasion of Poland forced Chamberlain's hand, and he declared war on 3 September, 1939. He soon came under attack from all political sides after the disastrous first months of war when Germany look set for a rapid victory. Unable to form a national government himself, he resigned in May 1940 after the failure of the British efforts to liberate Norway.

George VI asked Churchill to form a government in 1940 at the age of 65. Asking the House of Commons for its confidence in his small War Cabinet, he said: "I have nothing to offer but blood, toil, tears and sweat."

He was renowned as a great character and a great leader but was a paradoxical man. Possessed of astonishing vision, he also made disastrous mistakes - chiefly over the First World War battle at Gallipoli. Nevertheless, he brought Britain to victory against Germany on 8 May, 1945.

Following the Labour landslide in the post-war 1945 election, a surprised Churchill found himself leading the Conservative Opposition.

He then served in the Churchill war coalition as Lord Privy Seal despite Parliamentary Labour's strong pacifist contingent. In 1942 he was elevated to be Deputy Prime Minister and Secretary of State for the Dominions effectively in charge of domestic matters while the PM was occupied with the war.

After the war, Attlee's Labour Party was elected by a landslide - their offer to win the peace captured the national mood better than Churchill, promoted (justly) as the wartime hero. The Attlee government instituted a remarkable social and economic programme characterised by radicalism: the foundation of the National Health Service; the nationalisation of heavy industries and the Bank of England; a huge building programme; and a new national insurance scheme. In international affairs, the government oversaw the dismantling of Empire, the Berlin airlift during the Russian blockade of the city in 1948-9, and the formation of NATO.