Re: If the police or Home Office asks, they are ALREADY legally required to.
If, for example, the Home Secretary had decided that Home Office or Police should never ask for this data, then irrespective of the legal situation, this would not happen.
The police and other Home Office
goonscivil servants have generations of expertise, and specialist teams working 24/7 to apply it, in the specialist subject of "changing the Home Secretary's mind". That's why the National Identity Register keeps coming back from the grave - no matter how many times we think we've staked it, and regardless of which party is in power.