|Location Map ( geo)|
|Distance:||24.6 miles (39.6 km)|
|Meets:||A361, B4019, B4508, B4507, B4001, A338, A4, A34|
|Former Number(s):||A420, B4001|
|Route outline (key)|
The B4000 is a long rural B-road, running mostly in Berkshire.
It starts, however, over the border in the Wiltshire town of Highworth, at a roundabout on the southern edge of town, where it meets the A361 and B4019. From here it heads southeastward and quickly enters open country. Halfway to Shrivenham, and just before we cross the county boundary, the B4508 forks left, heading towards a junction with the A420 Watchfield bypass; our route, however, continues to Shrivenham, bridging the bypass and turning right to follow a brief section of the pre-bypass route of the A420 through the village before TOTSOing left to resume our southeasterly course.
The B4000 now crosses the western end of the Vale of White Horse. A bridge (built to replace an earlier level crossing) carries the road over the Great Western Main Line before the road goes through Ashbury and then starts to climb out of the valley. It skirts Kingstone Down before zigzagging into Lambourn, famous for its horses. The B4000 reaches a crossroads by the church where it TOTSOs right - but these roads are narrow and therefore signposts direct through traffic to take an earlier turn to follow some back streets to meet the B4000 slightly further south.
The road to the north of this crossroads is the B4001, which now multiplexes south along the B4000 for a couple of miles. After climbing Coppington Down the B4000 turns left on reaching a T-junction at Lambourn Woodlands to run parallel to the M4. The B4001 soon parts company with us by turning off to the right while the B4000 continues ahead to meet the A338 at Shefford Woodlands, just to the north of J14 of the M4. The old road through Shefford Woodlands having been bypassed, a leftward turn takes us briefly northeastwards along the A338 before we leave it by turning right and the B4000 regains its number and eastward direction.
The M4 is crossed about a mile further on and the B4000 then goes through some woods. After the village of Stockcross we reach a roundabout junction with the A4, where the rooute ends. This roundabout is part of a grade-separated junction providing access to and from the northbound A34 Newbury Bypass.
None of the above was numbered B4000 in 1922. Back then, the road started at the crossroads by the church in Lambourn and headed east along the River Lambourn, a route parallel to its current southern section. It went through East Garston before crossing the A338 at Great Shefford. It ended on the A34 (now B4494) on the northern edge of Newbury.
The road between Highworth and Lambourn was originally unclassified but it had become a western extension of the B4000 by 1932. This remained the situation for many years until it was decided to reroute the section between Lambourn and Newbury. The B4000 then took over a few miles of B4001 to end on the A4, at a junction that was altered with the coming of the A34 Newbury bypass, whilst the original route was declassified.