He doesn't need someone else in the car to report a driver for a red light and he doesn't need to show you the video.
Erm, you are very wrong. OK, the cop doesn't need a 2nd person to corroborate his own evidence, and nor does he need video evidence either. However, because the cop did state that the alleged offence was recorded on video, and that that video offence would be used in any court proceedings, then to withhold, when formally requested (and a verbal/oral roadside request is classed as a formal request) ANY evidence is in clear breach of PACE, because it is deemed an obstical to natural justice. So therefore, any legal proceedings where where refusal to supply evidence is rightfully claimed can be ordered to be thrown out by a Magistrate.
Some Cops really do need to appreciate that they are not above the law.
Also, have a look in the Highway Code for what an amber light means ... then think about if say the road was a 30mph road and you were doing 30mph how far you travel each second at that speed .... 13.4m. Factor in that each amber phase is normally 3 seconds. You would be 40m away from the stop line, if doing 30mph when the lights change to amber. 23m is the stopping distance in the Highway Code for 30mph (based on old tests) so if dong 30mph you should be able to stop without issues.
I am not suggesting you were speeding - you just need to be aware that if the lights were working correctly you can stitch yourself up by saying you were too close to stop, etc.
I agree with the Highway Code meaning for an amber traffic signal. Basically, amber means "STOP, only if it is
safe to do so". So whilst you are correct to advise caution about potentially stiching yourself up for speeding. However, and this is a big HOWEVER - the "STOP, only if it is
safe to do so" applies to all other road users who may be affected by your own actions. For example, if a car was tailgating you, or a car was approaching from the rear and you had real and genuine concerns that you would get whacked up the rear, then to stop on amber would be clearly unsafe, and it would therefore be lawful to go through an amber light. And this "safe/unsafe" dilemma is NOT formed by other road users - it has to be formed by the driver of the car in question.
Finally, all these traffic signal offences are ONLY valid for when the car actually and physically crosses the Stop Line. So in this instance, even if the video still proves you crossed the stop line during amber, but the lights changed to red before you had cleared the other side of the junction, then irrespective of all the above PACE advice, you can ask for the case to be dropped on the grounds that the cop is an unreliable witness (ie, the cop lied because he stated "crossed a red", when it was actually amber).
HTH