Question

a collection of official documents relating to British experiences​

Answer 1

Answer:

The official archives of the India Office Records are complemented by deposits of private papers relating to the British experience in India.

Answer 2

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British had preserved official documents, because they thought if they write and record everything, it will later be easier for them to study them and debate. They kept official records of what they thought was right, so that in the future, those records can serve as proofs of all the decisions that they had taken.