The B3421 is a short road in the eastern suburbs of Newbury. The road was originally unclassified but gained its number in the mid-1930s.
The road starts at traffic lights on the A4 Newbury Road and heads south over the River Kennet and through an industrial estate. It then bears right at a roundabout to head westwards. The railway line is to the left, although rarely visible, and the racecourse is on the far side of that.
We continue through the industrial estate then pass the entrance to Newbury Racecourse station. The road now becomes residential and it isn't long before we reach a one-way system. Traffic in this direction continues ahead along King's Road, which could be two-way were it not for the painted parking bays. Shortly a set of traffic lights is met where we TOTSO right (left is for Sainsbury's) and the road becomes two-way once more, ending at a signalised roundabout on the A339 town-centre relief road.
Eastbound traffic turns left off King's Road immediately after leaving the roundabout and follows Mill Lane, which is also residential with painted parking bays making the road one-way. We pass some offices and then bend sharply right onto Boundary Road, which takes us to a T-junction back on King's Road. Through traffic on the B3421 TOTSOs left here.