I agree with prudie, that puts a whole new light on it. I used to work in the field of employers' liability claims - their liability insurers wil almost certainly ask you to sign to release information from your medical records so they can assess your injuries. Are you claiming compensation through a solicitor or doing it yourself?
Incidentally if you have a claim in already, and you've written formally and it's been passed to their EL Insurance company, then your boss shouldn't be discussing the matter is with you at all, while the case is sub judice, otherwise it could prejudice the claim.