Encryption isn't going to help you get your data back if someone wipes the drive.
I don't understand how it can be legal for the police to wipe someone's drive if they haven't been convicted of anything, imagine it was paper documents (I assume) they wouldn't be allowed to black them out.
I don't think there's any possible way of getting back the lost data. I think he's onto preventative measures moving forward.
The Uk police undertake many illegal activities, as do the Uk government. What some departments seem to forget is the European court of human rights. There are quite a few systems in place which I'm fairly confident could be reasonably challenged in that court.
And then there are cases of blatant cover-ups where wrongdoing has taken place right up to and including the high court. (One that springs to mind involved the deaths of 96 football fans):
Hillsborough cover-up ‘worse than first thought’
This shit goes on all the time here. It's often not widely reported though.