Smart Motorway gantry sign
A gantry structure spanning the motorway with electronic signals, blue signs showing an exit and the following text.
Exit destinations: A41 Watford.
Forward destinations: (M1, M11), Aylesbury (A41); Luton [Airport symbol] Stansted [Airport symbol] M25 .
Junction number: 19.
There's only an exit at junction 19 heading clockwise, and it leads to a short spur road that will take you to Watford. Until 1986 the short spur was the main line of the M25, which terminated at Hunton Bridge roundabout; when the motorway was completed, it branched off here, leaving a little spur behind on its original course.