Make sure the photos have the time and date on, but also try to measure the full size of it with a tape measure on your photos, include the depth.
I got a friend to do a road bloack when i hit a pot hole to stop myself getting run over. Unfortunately for me the council filled in the hole the day after so they dismissed my claim, ended up with one trashed conti sport and BBS rc on my mk4 anni.
The council policy is to inspect every road a certain number of times and they should give you that info of when it was last inspected etc..
Good Luck