Motorway gantry sign
A gantry spanning the motorway with blue overhead signs indicating one lane exiting and three continuing ahead, and the following text.
Left lane destinations: M4 London; (W & C) ; The WEST; Slough Heathrow [Airport symbol]; Term 1, 2, 3 .
Right-hand three lanes destinations: (M3, M23, M20) Gatwick [Airport symbol]; Dartford; Heathrow [Airport symbol] (Term 4, 5 & Cargo) M25 .
Junction number: 15.
London's main road west crosses our path here - it'll take you to the west country, or Wales, or indeed anywhere else in the world if you use it to get to Heathrow.
The M25 here originally opened with no connection to the M4. The interchange between the two was so complex that it was only finished and opened to traffic the following year, in 1986.