Every legal argument I have been involved in had at least two lawyers (ie one for each side) so one of them had to be wrong.

He did say to destroy it was not an indictable offence. The code you refer to is about "wilful" destruction. I am pretty certain if he were to accidentally destroy (not negligently or recklessly) but purely accidentally it would not be an indictable offence. The evidential problems for the prosecution would be interesting to say the least.