|Distance:||50.5 miles (81.3 km)|
|Meets:||A6001, B1042, B1046, A428, A1198, A14, A1096, A1123, B1086, B1089, A141, B1096, B660, B1095, A605, B1167, A47, B1443, A16, B1166|
|Former Number(s):||B1041, B1086|
|Old route now:||A1096, B1166, B1173|
|Route outline (key)|
The B1040 is one of England's longest B roads. It's an important back road running through the Cambridgeshire and Lincolnshire Fens. It generally avoids any towns, skirting Huntingdon and Peterborough well to the east.
Originally, the B1040 was even longer, finishing on the A16 in Spalding. On 1st April, 1924, the northern section beyond Crowland was upgraded to become part of the A1073 although this section is now unclassified as it has been bypassed by the A16.
The section of the original route of the B1040 between Fenstanton and Warboys has also been altered. This section went across the mediaeval St Ives Bridge before leaving town to the northwest and going through Oldhurst en route to Warboys. After World War II, the route was severed by the Wyton Airfield runway and the B1040 was rerouted via Pidley, although the spur south of Warboys still remains to show the road's history. Then in the 1970s the section south of St Ives to Fenstanton was upgraded to become the A1096.
At the road's southern end it has taken over the former B1041 to give it a spur in Biggleswade.