I'd be tempted to send something much simpler:
Dear Transport for London,
I did not enter any box junction at 3:29 pm, nor did I come to a halt at 3:29 pm. All that can be established from the video is that I exited a box junction at 3:29 pm, so the allegation stated on the PCN did not occur.
Yours faithfully,
I like this. I'll submit it and cross my fingers.
I'll let you know how I get on.
My thanks to all those who contributed suggestions or critiques.
I'd be tempted to send something much simpler:
Dear Transport for London,
I did not enter any box junction at 3:29 pm, nor did I come to a halt at 3:29 pm. All that can be established from the video is that I exited a box junction at 3:29 pm, so the allegation stated on the PCN did not occur.
Yours faithfully,