Failure to provide information as to the identity of the driver is a
criminal offence.
Section 21(2)(a) of the 1991 Act.
The get out is:
(4) A person shall not be guilty of an offence by virtue of paragraph (a) of subsection (2) above if he shows that he did not know and could not with reasonable diligence have ascertained who the driver of the vehicle was.
Standard of proof (as I understand it) is 'no reasonable doubt' as to the failure to provide the information, but the wording of the getout is clearly designed to place the onus on you to demonstrate that you could not with reasonable diligince have found out who it was. And obviously the magistrate (was it a District Judge?) decided that you could have found out with reasonable diligence - whether that's justified, I know not
