Unlike Wavell, the new Attlee government in London saw its main priority as a rapid exit, winding up an overstretched empire that had long ceased to pay for its keep. Anxious to speed up the process, Attlee sent out the Cabinet Mission, led by Stafford Cripps, experienced in Indian politics and friendly to Nehru. The mission spent long months trying to reconcile the Congress goal of a majoritarian, unitary state with the Muslim League demand for effective safeguards and full autonomy for Muslim-majority provinces. The outcome was an ingenious three-tier scheme in which sovereignty would be shared in a pyramid, with individual provinces at its base, above them groups of provinces with either Hindu or Muslim majorities, and at the apex an All-India centre for defence and foreign affairs.

Had it been tried, the Cabinet Mission Plan would have been a unique constitutional experiment, more akin to the Holy Roman Empire than a modern nation state, but well suited to India's political realities. Both Congress and the League reluctantly accepted the plan, but then fell out over its precise interpretation. Poor Wavell spent the next six months battling unsuccessfully with Congress to honour the plan as originally accepted. His diaries record his growing exasperation with Gandhi and Nehru, as they tried to wriggle out of their earlier commitments. "What the Cabinet Mission intended and the way we interpret what they intended may not necessarily be the same," Gandhi told the viceroy at one such meeting. "This is lawyer's talk," said Wavell. "Talk to me in plain English. I am a simple soldier, and you confuse me with these legalistic arguments." To which Nehru quipped: "We cannot help it if we are lawyers." 

The coup de grâce for the Cabinet Mission Plan was delivered by Nehru in July 1946, when he publicly announced that a new constituent assembly, which would obviously have a large Hindu majority, would modify the plan as it pleased. The Muslim League promptly seized on this to back out as well, reiterating its demand for a separate Pakistan and launching direct action to achieve it.

Two of Nehru's closest colleagues have laid the blame for this breakdown squarely at his door. Maulana Azad, the leading Congress Muslim, called Nehru's press statement "one of those unfortunate events which changed the course of history", lamenting the fact that "he is at times apt to be carried away by his feelings". Sardar Patel too criticised Nehru for acting "with childlike innocence, which puts us all in great difficulties quite unexpectedly". Nehru himself maintained that he had acted out of the conviction that partition was preferable to a loose federation. The union proposed by the Cabinet Mission Plan "would be a very weak India; that is a federal India with far too much power in the federating units. A larger India would have constant troubles, constant disintegrating pulls."

Nehru wanted instead to be master in his own house, free to implement his socialist policies through centralised economic planning; and the Muslim League, in control of large, autonomous provinces, would have been an unwelcome brake on all this. Most important of all was Nehru's visceral hatred of Jinnah, recorded with brutal candour in his diaries:

"Jinnah . . . offers an obvious example of an utter lack of the civilised mind. With all his cleverness and ability, he produces an impression on me of utter ignorance and lack of understanding and even the capacity to understand this world and its problems. . . . Instinctively I think it is better to [have] Pakistan or almost anything, if only to keep Jinnah far away and not allow his muddled and arrogant head from interfering continually in India's progress."