Photos are not a legal requirement, but TfL have provided two frame from their video record. Their letter says their video will be supplied under separate cover. These are sent by post as a DVD, and if they have processed the matter correctly, the enforcement process is put on hold for about 14 days. Check the PCN status to see it is no hold and a DVD is to be sent. If in doubt phone them.
Enforcement is a civil law matter, so the test of the contravention occurring is "on the balance of probabilities", and this is what will be applied by an adjudicator at London Tribunals. TfL will say you were there and show the video, so what will you say, "it wasn't my car" or "the numberplate has been misread" or what ?
The contravention time is 17.55, well within the restricted times.