174 Box junctions. These have criss-cross yellow lines painted on the road (see 'Road markings'). You MUST NOT enter the box until your exit road or lane is clear. However, you may enter the box and wait when you want to turn right, and are only stopped from doing so by oncoming traffic, or by other vehicles waiting to turn right. At signalled roundabouts you MUST NOT enter the box unless you can cross over it completely without stopping.
We have some particularly noxious box junctions in our fair city which often get themselves into all sorts of trouble due to people forgetting these fairly simple rules. The worst is probably this one which is plagued both by drivers coming up the dual carriageway queuing across it but also, and much worse for traffic flow, busses turning right from the east of the picture not understanding that while they are allowed into the box they are not suppose to stop diagonally all the way across it blocking people from crossing the junction in any direction.
There are many things painted on our roads that may not be necessary for their safe and efficient use (Kensington and Chelsea have created a lot of comment being minimalist on the High Street). I also understand that there are often junction layouts where things seem to have been put their because the town planner hates drivers. I really don't think box junctions are necessarily one of these things and certainly not in this particular case. People could do well in understanding that just sometimes these road markings are in place to help and not the mark of an oppressive state.