Must I give way to a filtering car?

[lacmag3]

I'm in heavy, slow-moving traffic, in the left lane having exited from a roundabout. The right lane last only 150 yards before filtering in to the left. The right lane is empty until someone speeds down its length and needs me to brake to allow him/her in (we're all travelling relatively closely because of our lack of speed in the left lane). The driver gets annoyed when I don't brake to let him/her in. Am I just being pigheaded or both pigheaded and falling foul of the law??

[Paul22118]

On the main A21 road towards Eastbourne, around Tonbridge I think, there is a dual carriagedway which turns into a single lane. Just beyond the end point there is a road that then merges from the left. The dual carriageway is national speed limit and the traffic flow is often very heavy, consequently there is much hard braking as there is invariably a tail back from the left hand lane that has now slowed down to proceed forward into a single lane.
This means the outside lane is often and inexcusably either empty or much less congested. It is correct therefore that all drivers should use both lanes and filter every other at the queue head thus allowing maximum progress of everyone. The tantrums, pigheaded or otherwise, of those who have 'chosen' to drive in lane one when passed by others in the less congested lane two, is a sight to behold. Some swerve like a F1 car to stop others passing. Some go as far to the left as they can without reliquishing their position in lane one and I have even seen some drivers drive along slowly with the drivers door open fully to increase the width of their car.
So in answer to you question it is somewhat pig headed not to allow another to join the narrowing lanes - FOR BOTH OF YOU - and certainly not good and safe practise. If all drivers were to use both lanes and merge in turn there would be no issue at all, ever. The Highway Code says drive on the left BUT that applies when the road is clear. If the lane one is full and lane two is available and empty - use it. If one did not do this the tail back would go back many miles with lane two empty and unused. Silly.