Or are you suggesting that the light phase for the lorry would remain green whilst the light changes to green for the carriageway perpendicular to it (the one with the cyclists on it)?
I don't know if we are even looking at the same video, but here goes:
At 14 seconds in, the cyclist is moving, across the white stop line and past the light on first light on the lamp post. It is at red. The boris bike has just cleared the stop line on their part of the junction. The lorry is half a second away. At this point, there is no evidence either way whether his light is red or amber. At the point the cyclist's light goes red & amber the lorry can be seen to a couple of feet short of the red stop line. Therefore the light is undeniably red when he goes through it - the red/amber will not come on unless the other light is red, but there is no evidence to see for how long it has been so .. I don't know how long it has been red for and neither do you. He is therefore undeniably commiting an offence. The cyclist is now well beyond the stop line and well past the first traffic light. He too is committing an offence. He is compounding that error by paying absolutely no attention to the traffic around him. This is why he cycles into the side of the lorry. It is, from a legal standpoint, immaterial whether the lorry goes through the red after it is red for 0.1 or 3 seconds, he has been guilty of an offence* by making no attempt to stop on amber. However, the reason why the incident happened is because the cyclist showed an incredible lack of awareness of the traffic. Let's get hypothetical here. It is is entirely possible that the lorry's light went to red at the same time as the cyclist's went red/amber. That is often how light phases work. If the lorry had beeen five feet further forward in that event , the driver would not have been going through a red (He still made no attempt to stop at amber), but the cyclist would still have gone into the side of him. In fact there is a good 15-20 feet of lorry for the bloke to avoid. To me the lorry driver is driving in a (sadly) averagely bad manner, the cyclist is cycling spectacularly poorly. There are quite a few cyclists in the video who are technically committing an offence at that junction. Only one manages to go into the side of the lorry.
* maybe TC can help out here, but I get the feeling that if someone goes through a red fractionally after it has changed, they are seen as less culpable by the courts (careless raher than dangerous?) than if they do so when it has been red for several seconds. It is noticeable that our boy on the bike starts moving 3 seconds before his light goes green.