The UP fiasco of 1937 was the key turning point in Muslim separatism and the radicalisation of its urbane and very anglicised leader, Jinnah. A more unlikely founder of a theocratic Islamic state is hard to imagine than this Edwardian barrister, with his London education and immaculate Savile Row suits, his love marriage to a glamorous, non-Muslim socialite and his total disregard for any Islamic religious rules. Back in 1916, when the Congress and the Muslim League agreed on an anti-British pact, it was Jinnah who had been its chief architect, hailed by the Hindu leaders of Congress as "the ambassador of Hindu-Muslim unity".

What turned this secular-minded, pro-Congress Muslim into the sectarian separatist of the 1940s? Two of his most recent biographers, Ayesha Jalal, a Pakistani-American academic, and Jaswant Singh, a former Indian foreign minister, have converged on the same answer: it was the arrogance and intransigence of Congress leaders — Nehru in particular — and the blatant pro-Nehru bias of the last viceroy, Mountbatten. "Partition was the last thing Jinnah wanted," says Jalal, and she agrees with Singh that his demand for it was essentially a bargaining ploy. 

Following the outbreak of the Second World War, Congress, in a fit of pique about not being consulted, pulled out of provincial ministries and rejected British attempts to cajole it into a less than fully independent central government. Instead Congress launched the Quit India movement, which landed most of its leaders and active cadres in jail for the rest of the war. It was a spectacular own goal, because Jinnah filled the political vacuum, dramatically expanding his power base across India's diverse Muslim communities. 

It was not until 1940 that the Muslim League formally adopted the goal of Pakistan, in a vague resolution which left wide open whether it would be a single or multiple entity, a sovereign state or an autonomous state within a state. Jalal emphasises that Jinnah's two-nation theory was not a territorial concept, but a demand for parity between Hindus and Muslims within the same borders. Most Indian Muslims, after all, were minorities in Hindu-majority provinces, while the Muslim-majority provinces themselves depended heavily on the commercial and professional skills of their prosperous Hindu minorities. 

At the end of the war, constitutional negotiations resumed in earnest between Congress, the Muslim League and the viceroy, Field Marshal Lord Wavell, a remarkable soldier-statesman with long Indian experience. His role has been much misunderstood by nationalist Indian historians, who have blamed him for favouring the Muslim League and using divide-and-rule tactics. But his key objective was to transfer power to a united India, and he was determined that Britain must stay on until it could broker a workable deal between Congress and the League.