Why and how did the British follow the policy of 'Divide and Rule' in India?

After the Revolt of 1857, the British followed the policy of "divide and rule" to keep themselves in power by causing rift between various sections who could otherwise unite against the British. They did this in the following manner:

1. The British encouraged communal and separatist trend in Indian politics.
2. They sowed the seeds of disunity between the Hindus and the Muslims. The British suppressed the Muslims systematically and they were treated with suspicion.
3. After the Congress came into picture, the British started hating the Hindus too.
4. The Government tried to keep the Muslims aloof from the Congress. Sir Syed Ahmed Khan and Theodore Beck tried to convince the Muslims that Congress was a Hindu organisation.
5. Partition of Bengal was a clear example of the application of the policy of Divide and Rule.