[mothered]

It's just a document from beaverbrooks themselves, stating that after signing it they can start the investigation.
Filled it out and sent it back to them. They've forwarded it to their boss and he will reply on Monday.

In that case, It's not legally binding and you did the right thing by signing It.

If they had reason to decline your claim, It would've already been done, so It's looking promising thus far.