was built as a bypass to relieve traffic congestion in Brentford and Hounslow. After the A30, the A4 changes its name to Bath Road, enters Cranford, and crosses the River Crane into the Borough of Hillingdon. It then passes along the northern boundary of Heathrow Airport, before leaving the London suburbs over the M25 towards the west. Heathrow Airport to Slough (6.7 miles) 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. Slough to Maidenhead (6.0 miles) Continuing from the William Street / Wellington Street junction, in the centre of Slough, the road heads westwards towards Maidenhead. The short stretch of dual carriageway is Wellington Street, then briefly on the most western end of the High Street, over the railway bridge for the line between Slough and Windsor Central Station. The Bath Road begins on the west side of the bridge. On the left is Slough's 1936 Town Hall, now abandoned by the local council, and on the right Salt Hill Park. The next major road intersection is by the Three Tuns Pub where the A4 crosses the A355. This road goes north towards Farnham Royal, Farnham Common, Beaconsfield and the M40 at junction 2. To the south, it goes