The B1421 is a surprisingly rural B-road in south Essex. The road was originally unclassified but gained its number in the early 1930s.
The road starts at a signalised crossroads in the centre of Upminster where four differently numbered roads meet. West is the A124, east the B187, north is an unclassified road past the station to the A127, and the B1421 heads south. After passing shops and a recreation ground the road becomes residential and we continue south along Corbets Tey Road. Presently the road climbs to a sharp left-hand bend, after which a couple more bends take the road past Upminster Cemetery and into open country.
We continue east across the fields and then go over the Upminster to Grays railway line and then the M25 in quick succession. We now enter the scattered village of North Ockendon where we end at a T-junction on the A186.