Are you obliged to stop driving in this situation?

In the video you are approaching a junction with traffic lights in a town; the traffic lights show green, and in the middle of the junction a police officer is standing with his back to you. In this situation you must refrain from moving. The answer is: yes.

The Road Traffic Act states that instructions and signals given by persons directing traffic take precedence over light signals and road signs. The Regulation on road signs and signals states that a position in which the person directing traffic is facing the approaching vehicles with his front or back means a ban on entering the junction or the stretch of road beyond the person directing traffic. The green light would allow you to enter, but in the hierarchy of signals the police officer is higher: since you can see his back - and the back and the front mean the same - traffic is closed for you, and you stop before the junction, just as you would at a red light. You only move off when the police officer turns sideways to you. The traffic lights may keep working, but when a police officer is directing traffic, you look at him, not at the traffic lights.

Legal basis: Art. 5 para. 1 and 2 of the Road Traffic Act (Prawo o ruchu drogowym); § 108 para. 1 and 3 of the Regulation on road signs and signals