The A421 will carry the weary traveller from a point near Banbury to Milton Keynes, Bedford and St Neots, a country road through the villages and towns of Buckinghamshire and Bedfordshire.
The expressway between those points is relatively new, and as recently as 1995 Bedford was an important county town stranded between the M1 and A1 with no particularly good connection to either. Since 1996, three sections of new dual carriageway have been built, progressively completing a fast route that serves to link Cambridge to Milton Keynes and Bedford to the wider world.
As good as this new expressway is, it's let down by its two terminal junctions - both of which, in fact, feature in our Bad Junctions list. The Black Cat Roundabout is just a nasty flat roundabout that's been overloaded for years, but particular merit is awarded to M1 J13 Ridgmont Interchange which was modified in 2010 from a tiny diamond junction to the monstrous calamity that stands there today. A fast new road surely deserves better connections to the rest of the road network than these.
It's hard to escape the fact that much traffic on this road continues east of St Neots to reach Cambridge and the A14, and that at least half of that is also a high-quality, brand-new expressway. There's only nine miles, as the crow flies, between the end of this road at Black Cat and the start of the A428 expressway at Caxton Gibbet.
You're not looking at the whole A421
This page is about the parts of the A421 that are designated a motorway or that have motorway characteristics. Other sections of this road will not be featured here and will not count towards the length of the road as shown below.