Well, that's what you get for not running a totalitarian country.

By and large, it's a feature, not a bug, that the government isn't sharing all the information it has between its various parts.

Eg GCHQ has lots of information it has (ostensibly) for keeping the country safe, but that doesn't mean that the prosecution in a criminal case should get access to all the same information.

Of course, that's a bit inefficient and duplicates efforts. But such is a price for restrained government.