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Location Map ( geo)
Cameraicon.png View gallery (44)
From:  Barleymow Roundabout, Brackley (SP577334)
To:  Black Cat Roundabout, Roxton (TL159553)
Via:  Bedford, Milton Keynes
Distance:  44.4 miles (71.5 km)
Meets:  A43, B4031, A4421, A413, B4033, B4034, A4146, M1, A507, A6, B531, B530, A5141, A600, A603, A4280, A1
Former Number(s):  B4031, B4034, B557, A428
Old route now:  A34, A41, A4421
Primary Destinations
Highway Authorities

National Highways • Buckinghamshire • Central Bedfordshire • Milton Keynes • West Northamptonshire • Oxfordshire

Traditional Counties

Bedfordshire • Buckinghamshire • Northamptonshire • Oxfordshire

Route outline (key)
A421 Weston-on-the-Green – Finmere
A421 Barleymow Roundabout – Black Cat Roundabout
A421 Black Cat Roundabout - Caxton Gibbet Roundabout

The A421 is a major east-west road that forms part of the main route between Oxford and Cambridge (via Milton Keynes and Bedford.) It could be seen as having fallen on hard times, as it has now lost a good few miles of its original route, although in compensation it has been greatly extended at its eastern end.


A421 approaching Bedford

Today's route starts at the Barleymow Roundabout on the A43, just south of Brackley. This road was the B4030 but has now assumed a more important guise. From here the road makes the short journey to Finmere where it meets its old route. The road generally follows the B4030 route except for a new section just to the south-west of Mixbury and for the final part before meeting the A4421 at the Finmere Airfield roundabout.

Finmere and its neighbour Tingewick have now been bypassed with a high quality dual carriageway in part, somewhat out of place in my opinion. Quickly we arrive at the western end of the Buckingham bypass and traverse this by five roundabout junctions, including one with the A413 with which the road multiplexes for one section. The road then follows a new alignment for around 500 metres before joining the old route of the B4034. Originally, Buckingham (and the A413) marked the eastern end of the A421.

After the roundabout with the B4033 from Winslow. The road has been largely improved to a good standard, and we start to cross Whaddon Chase. As the road approaches Tattenhoe and Far Bletchley, the original B4034 takes the route to Bletchley, whilst the A421 adopts the guise of H8 (Standing Way). We cross the A5 without a junction (a spur leads off to a GSJ on the A5 from the next roundabout) and head through the outskirts of Milton Keynes towards the M1, crossing it via junction 13. This section has been upgraded to dual carriageway in a piecemeal approach during the 2000s/10s, with the final link being completed in 2020, connecting Milton Keynes by a continuous dual carriageway to the M1 at J13.

The final stretch runs from junction 13 of the M1 to the Black Cat roundabout on the A1. As such it is an important trunk route linking the A1 and M1. Moreover a little further north on the A1 is the A428 which joins up with the A14. This forms a continuous route from the East-Anglian Ports to the South Midlands and also form a relief road to the M25.

The M1/A421 interchange has been updated, completed in 2012, to cope with a higher volume of traffic, and encourage the use of routes such as the A507, which now also has access to the M1 from that junction.

The road was also dualled between the M1 and the Bedford bypass, where there are several large distribution centres. This project opened in December 2010 and included an upgrade of the Bedford southern bypass, which was opened in the late 1990s as single carriageway. It is now dual-carriageway throughout with grade separated junctions with other routes, such as A6. Shortly after this the only significant landmarks on the road come into view. These are the massive hangers that were built in the 1930s to house airships.

After the Bedford bypass we're on the Great Barford Bypass (which opened as a separate scheme in 2006), running from Bedford to the Black Cat.


The original start of the A421 on what was then the A43

Originally, the road started at the current A34 and B430 junction at Weston-on-the-Green. Back then this was a simple fork, which later became a roundabout, with the single-carriageway A43 from Oxford to Northampton. From here the road runs virtually straight towards Bicester, passing Wendlebury on its way and arriving into Bicester from the south. Through Bicester it became a slow moving road through the town, meeting the A41 (now B4100) in the centre. It then escaped north under the Marylebone–Banbury railway line and out towards Newton Purcell. The road becomes quite wide here due to an age-old improvement. It then dived under the now-disused Great Central Railway at Finmere Station. The road, still following a straight course, arrived at Finmere, site of a huge market on the old airfield.

The old route has now changed, dramatically in some places. From Weston on the Green the road is now the dual carriageway A34 link to the M40. From there it is dualled all the way to the Bicester bypass and is part of the re-routed A41. Indeed, the A421 south of Bicester had become a spur of the A43 by the mid-1940s but regained the A421 number in the 1960s. North of Bicester the road has been imaginatively renumbered the A4421.


The A421 is going to receive a new D2 expressway section between the Black Cat Roundabout and the Caxton Gibbet Roundabout to upgrade the existing S2 A428 as part of the A428 black cat to caxton gibbet scheme, which is due to be completed in 2026. The Black Cat Roundabout will be replaced with a 3 tier junction with the A1 with the A421 becoming a flyover, the A1 passing under a new roundabout, a new junction built to connect with the existing A428 and St Neots, and another junction with the A1198 to replace the Caxton gibbet roundabout.


BBC News

National Highways

Related Pictures
View gallery (44)
A421 for another 2 hours - Coppermine - 12843.jpg421 - Half open - Coppermine - 12839.jpgHalf the A421 - Coppermine - 12835.jpgSouthern Road Schemes - Coppermine - 6939.PNGBedford Southern Bypass - Geograph - 2462783.jpg
Other nearby roads
Milton Keynes
NCN51 • A5 • A50 • A422 • A506 (Hockliffe - Northampton) • A508 • A509 • A4146 • A5130 • B488 • B526 • B557 • B4033 • B4034 • C5 (Milton Keynes) • C9 (Milton Keynes) • C13 (Milton Keynes) • C24 (Milton Keynes) • C41 (Milton Keynes) • C129 (Milton Keynes) • C130 (Milton Keynes) • C131 (Milton Keynes) • C132 (Milton Keynes) • C140 (Milton Keynes) • C141 (Milton Keynes) • C142 (Milton Keynes) • C143 (Milton Keynes) • C144 (Milton Keynes) • C145 (Milton Keynes) • C146 (Milton Keynes) • C147 (Milton Keynes) • C149 (Milton Keynes) • C150 (Milton Keynes) • C151 (Milton Keynes) • C152 (Milton Keynes) • C154 (Milton Keynes) • C155 (Milton Keynes) • C156 (Milton Keynes) • C157 (Milton Keynes) • C158 (Milton Keynes) • C159 (Milton Keynes) • C160 (Milton Keynes) • C162 (Milton Keynes) • C179 (Milton Keynes) • C181 (Milton Keynes) • E13 • E31 (via Carlisle) • E33 (London - Glasgow) • H1 (Milton Keynes) • H2 (Milton Keynes) • H3 (Milton Keynes) • H4 (Milton Keynes) • H5 (Milton Keynes) • H6 (Milton Keynes) • H7 (Milton Keynes) • H8 (Milton Keynes) • H9 (Milton Keynes) • H10 (Milton Keynes) • Holyhead Road • M1 • T11 (Britain) • V1 (Milton Keynes) • V2 (Milton Keynes) • V3 (Milton Keynes) • V4 (Milton Keynes) • V5 (Milton Keynes) • V6 (Milton Keynes) • V7 (Milton Keynes) • V8 (Milton Keynes) • V9 (Milton Keynes) • V10 (Milton Keynes) • V11 (Milton Keynes) • V12 (Milton Keynes) • Watling Street
NCN51 • A6 • A418 • A422 • A428 • A600 • A603 • A4280 • A5134 • A5140 • A5141 • A6002 (Bedfordshire) • A6172 (Bedford) • B530 • B531 • B557 • B560 • B561 • B562 • B563 • B564 • B659 (Bedford) • B660 • B5379 • C4 (Bedford) • C5 (Bedford) • C8 (Bedford) • C11 (Bedford) • C12 (Bedford) • C15 (Bedford) • C22 (Bedford) • C26 (Bedford) • C28 (Bedford) • C32 (Bedford) • C40 (Bedford) • C43 (Bedford) • C44 (Bedford) • C45 (Bedford) • C46 (Bedford) • C47 (Bedford) • C53 (Bedford) • C54 (Bedford) • C56 (Bedford) • C70 (Bedford) • C79 (Bedford) • C81 (Bedford) • C82 (Bedford) • C94 (Bedford) • C127 (Bedford) • C156 (Bedford) • C208 (Bedford) • C402 (Bedford) • C405 (Bedford) • C425 (Bedford) • C501 (Bedford) • C510 (Bedford) • C511 (Bedford) • C512 (Bedford) • C515 (Bedford) • C519 (Bedford) • C523 (Bedford) • C524 (Bedford) • C531 (Bedford) • C545 (Bedford) • C546 (Bedford) • C551 (Bedford) • C553 (Bedford) • C560 (Bedford) • C561 (Bedford) • C562 (Bedford) • E24 • E28 (Birmingham - Ipswich) • T12 (Britain) • T45 (Britain)
St Neots
A400 • A401 • A402 • A403 • A404 • A405 • A406 • A407 • A408 • A409 • A410 • A411 • A412 • A413 • A414 • A415 • A416 • A417 • A418 • A419
A420 • A421 • A422 • A423 • A424 • A425 • A426 • A427 • A428 • A429 • A430 • A431 • A432 • A433 • A434 • A435 • A436 • A437 • A438 • A439
A440 • A441 • A442 • A443 • A444 • A445 • A446 • A447 • A448 • A449 • A450 • A451 • A452 • A453 • A454 • A455 • A456 • A457 • A458 • A459
A460 • A461 • A462 • A463 • A464 • A465 • A466 • A467 • A468 • A469 • A470 • A471 • A472 • A473 • A474 • A475 • A476 • A477 • A478 • A479(W) • A479(E)
A480 • A481 • A482 • A483 • A484 • A485 • A486 • A487 • A488 • A489 • A490 • A491 • A492 • A493 • A494 • A495 • A496 • A497 • A498 • A499
Defunct Itineraries & Motorways: A403 • A404(M) • A405 • A407 • A423(M) • A430 • A437 • A446(M) • A455 • A464 • A475 • A491

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