After leaving Heathrow Airport, still the A4, it becomes the Colnbrook Bypass and climbs over the M25 motorway.
This bypass for the narrow main road of Colnbrook was built after the Second World War across farmland between Harmondsworth and the outskirts of Langley.

The next major intersection is junction 5 of the M4 (Slough-East) known as the Langley junction.
At this point the A4 loses its trunk road classification.

Continuing towards Slough town centre, the road, now named London Road, passes Kedermister Park on the right.
Changing into Sussex Place, the architecturally impressive St Bernard's former convent is on the right.
Becoming the dual carriageway Wellington Street (a late 1960s bypass for the High Street), Tesco's massive 'aircraft hangar' supermarket is on the right and the Queensmere and Observatory Shopping Centres on the left.

The end of this section of the Great Western Road is in the centre of Slough at the junction of William Street and Wellington Street.
This spot was formerly the site of Slough's largest roundabout on the south-east corner of Thames Valley University.
Nearby is Slough railway station, served by Great Western Railway.

The roundabout was removed in 2011 and the university's Slough campus closed in 2011 after planning permission was granted for 1,598 flats.
After leaving Heathrow Airport, still the A4, it becomes the Colnbrook Bypass and climbs over the M25 motorway. This bypass for the narrow main road of Colnbrook was built after the Second World War across farmland between Harmondsworth and the outskirts of Langley.
The next major intersection is junction 5 of the M4 (Slough-East) known as the Langley junction. At this point the A4 loses its trunk road classification.
Continuing towards Slough town centre, the road, now named London Road, passes Kedermister Park on the right. Changing into Sussex Place, the architecturally impressive St Bernard's former convent is on the right. Becoming the dual carriageway Wellington Street (a late 1960s bypass for the High Street), Tesco's massive 'aircraft hangar' supermarket is on the right and the Queensmere and Observatory Shopping Centres on the left.
The end of this section of the Great Western Road is in the centre of Slough at the junction of William Street and Wellington Street. This spot was formerly the site of Slough's largest roundabout on the south-east corner of Thames Valley University. Nearby is Slough railway station, served by Great Western Railway.
The roundabout was removed in 2011 and the university's Slough campus closed in 2011 after planning permission was granted for 1,598 flats.
A4 road (England)