Could you imagine
There are three reasons that the M25 is a constant mess:
1. Most of it is five lanes... alot of it was designed as three lanes, so at most junctions rather thasn rebuilding them, they simply lost the left hand lane (or two), which forces jams where you have five lanes of traffic being forced into three or four.
2. Alot of people do what Tunnie suggests, which blocks the junctions up and then forces people already on the motorway to brake because the joining traffic chooses to shove straight back into lanes two and three.
3. That particular section has five junctions in ten miles which compounds the problem. So whilst junction 11 might be a bit slow, by the time you get to junction 15, everything is at walking pace. Going the other way the junctions are reversed, but the effect is the same.
The funny thing is, Tunnie doesn't actually need to even use the motorway to get to work