Question

why does British preserve official documents

Answer 1

For their work,,,in this they store essential files of land ec.

Answer 2

$\huge\mathbb{ANSWER}}$

One important source is the official records of the British administration. The British believed that the act of writing was important. Every instruction, plan, policy decision, agreement, investigation had to be clearly written up. Once this was done, things could be properly studied and debated.