Of course they are trying it on, (as usual !!). The person who claims to have viewed this video maybe needs to go ot Specsavers !
You should submit reps stating that the contravention did not occur, because the video shows the vehicle never stopped. Don't be surprised if they reject because they rely on >95% of people then coughing-up, not wanting to risk the extra dosh involved in going to London Tribunals.