Just to build on Neil's response, the key part of the contravention wording is that you "had to" stop due to stationary vehicles. We frequently win cases where the council sends a PCN but the video shows sufficient space for a car, which is stationary in the box junction, to be able move forward and exit the box. I.e. it stopped in the box junction but it didn't have to.
In your case, the video is opaque as to how much space you left in front. I estimate you were only in the box by around one wheel diameter (which for a Renault Clio I believe will be around 40 cm). It's for the council to prove you committed a contravention so I'd like to think that a fair minded adjudicator would agree there is insufficient evidence you "had to" stop where you did. The test is on the balance of probabilities so you would only need to create sufficient doubt as to this fact rather than prove your case.
40 cm is not very long, and I would suspect, unless you had deliberately got as close as possible to the vehicle in front as you knew you were likely to encroach into the box junction, that you would routinely leave at least 1 metre to the car in front. Most cars these days have distance sensors which would enable you slowly to creep forward very closely to the car in front without fear of an actual collision meaning you could have fairly easily moved closer and out of the box if you had realised you had left your back wheel inside.
The council will never accept this argument, so your choices will be either to settle at £65 while the discount is still available, or take it to the tribunal where it's £0 if you win and £130 if you lose.
