Was the creation of Pakistan pre-planned by the British?

The first time I heard that Pakistan was a creation of the British was in 1984. A retired government official told me that Pakistan was created so that the British would have an excuse to create Israel a few months later. After that, I heard a speaker of the Jamat-e-Islami say that Pakistan was not achieved by Jinnah. According to him, the British wanted a buffer state to prevent the Soviet Union from expanding southwards. They believed that Nehru and Gandhi would never help them. That was why Jinnah was never sentenced to a jail term, like Hindu leaders Gandhi and Nehru. Indians use this fact to say that Jinnah was an agent of the British.

Nowadays, with Israel killing Muslims with impunity, there are voices again saying that the British had planned the creation of Pakistan as early as the 1920s. They wanted India to be broken up into Hindustan, Pakistan and Princestan (a state that would be ruled by the princes).

I find it very hard to believe all this. As late as 1946, Jinnah was prepared to keep India united. Nehru and the others did not accept his demand for more seats for Muslims in the assemblies. The British Viceroy Mountbatten did his utmost to keep India united, which disproves that the British wanted to break up India.