Motorway gantry sign
A gantry spanning the motorway with blue overhead signs indicating two lanes exiting and three continuing ahead, and the following text.
Left-hand two lanes destinations: M3 The SOUTH WEST; Southampton; London, Richmond .
Right-hand three lanes destinations: (M23, M20), Woking (A320); Gatwick [Airport symbol] Dartford M25 .
Junction number: 12.
The signs approaching this junction will tell you the left-hand two lanes go to The SOUTH WEST and Southampton, and they do it for much longer than the one mile's notice offered at most junctions. But then as soon as the sliproad breaks away from the M25 they pull the rug out from under you, revealing that the left lane goes only to London, and everyone wanting the M3 westward has to suddenly merge into a single lane.