Something on these lines: -
Dear Sirs
PCN <pcn number> dated <date> for location <location details> - Failing to comply with a prohibition on certain types of vehicles
I refute the above alleged contravention on the grounds that the contravention did not occur.
Your video does not show my vehicle passing any applicable restriction signs. I therefore request that the PCN be cancelled forthwith.
Yours faithfully
It's best not to write too much; let them do the work. They will, of course, reject your reps. Post the rejection when you get it, and we can see if it's worth going to London Tribunals. The signs in the video only apply to vehicles travelling in the opposite direction.
