London became the largest and most populous metropolitan area in the world during the Victorian era, and trade within the British Empire – as well as the standing of the British military and navy – was prestigious. Political agitation at home from radicals such as the Chartists and the suffragettes enabled legislative reform and universal suffrage. Power shifts in east-central Europe led to World War I; hundreds of thousands of English soldiers died fighting for the United Kingdom as part of the Allies. Two decades later, in World War II, the United Kingdom was again one of the Allies. At the end of the Phoney War, Winston Churchill became the wartime Prime Minister. Developments in warfare technology saw many cities damaged by air-raids during the Blitz. Following the war, the British Empire experienced rapid decolonisation, and there was a speeding up of technological innovations; automobiles became the primary means of transport and Frank Whittle's development of the jet engine led to wider air travel. Residential patterns were altered in England by private motoring, and by the creation of the National Health Service (NHS) in 1948. The UK's NHS provided publicly funded health care to all UK permanent residents free at the point of need, being paid for from general taxation. Combined, these changes prompted the reform of local government in England in the mid-20th century.