u/Melodic-Baseball-279

Driving on M25 and there is a sign with the number 40 in it, in a red circle and next to it there is a sign that says 'possible congestion' (i can't remember the exact wording.)

Anyway I am in the far left lane and go down to 40mph but then lorries get up close then overtake - am I doing something wrong?

Also I saw a lorry in the far right lane the other day on M25- is that legal?