Highway code – Roundabouts

Rule 185

When reaching the roundabout you should

give priority to traffic approaching from your right, unless directed otherwise by signs, road markings or traffic lights
check whether road markings allow you to enter the roundabout without giving way. If so, proceed, but still look to the right before joining
watch out for all other road users already on the roundabout; be aware they may not be signalling correctly or at all
look forward before moving off to make sure traffic in front has moved off.