Overtaking in the UK
ON NON-MOTORWAYS - Rule 163 of the Highway Code states only overtake on the left if the vehicle in front is signalling to turn right, and there is room to do so stay in your lane if traffic is moving slowly in queues. If the queue on your right is moving more slowly than you are, you may pass on the left.
ON MOTORWAYS - Rule 268 of the Highway Code states – do not overtake on the left or move to a lane on your left to overtake. In congested conditions, where adjacent lanes of traffic are moving at similar speeds, traffic in left-hand lanes may sometimes be moving faster than traffic to the right. In these conditions you may keep up with the traffic in your lane even if this means passing traffic in the lane to your right. Do not weave in and out of lanes to overtake.
Is overtaking on the left an offence?
Overtaking on the left is lawful if done in accordance with the above guidance. However, whilst there is no specific offence of overtaking on the left, if a driver undertook another vehicle, other than in the circumstances described above e.g. in the case of someone hogging lane 2 on a motorway, they may be prosecuted for careless driving.
The United Kingdom is the only set of countries in Europe which marks the speed limits and distances in miles rather than kilometres. Traffic on a roundabout has priority, you will find roundabouts to be much more prevalent in the UK than other parts of the world.
Priority is marked at junctions. If a driver is giving way to you they will often flash their lights to signal that you can go ahead. Give way to any emergency services vehicles such as ambulances and police cars with flashing lights.