The River Flit is a short river in Bedfordshire

Bedfordshire

Bedfordshire is a ceremonial county of historic origin in England that forms part of the East of England region.It borders Cambridgeshire to the north-east, Northamptonshire to the north, Buckinghamshire to the west and Hertfordshire to the south-east....

, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. It flows through Flitwick

Flitwick

Flitwick, pronounced , is a small town and civil parish in Central Bedfordshire, England. The nearby River Flit runs through Flitwick Moor, a nature reserve and a Site of Special Scientific Interest.-Location:...

, then past Greenfield

Greenfield, Bedfordshire

Greenfield is a small village about from the town of Flitwick in Bedfordshire, England.It lies across Flitwick Moor from the larger town and is on the opposite side of the River Flit. It forms part of the parish of Flitton and Greenfield. Due to closures, there is now only one public house in...

 and Flitton, then through Clophill

Clophill

Clophill, is a small village and civil parish located in the Flit river valley, Bedfordshire, England. At this time the village belonged to a group of two or three hamlets – Beadlow, Cainhoe and possibly Moddry.It is recorded in the Domesday Book of 1086 as Clopelle; meaning tree-stump Hill in old...

, Chicksands

Chicksands

Chicksands is a village in the Central Bedfordshire district of Bedfordshire, England and part of the civil parish of Campton and Chicksands . It is on the River Flit. Nearby places are Shefford and Campton....

, and Shefford

Shefford, Bedfordshire

Shefford is a small town and civil parish located in the Central Bedfordshire district of Bedfordshire, England. At the 2001 census it had a population of 4,928, although this was estimated to have grown to 5,770 by 2007.-History:...

, then past Stanford

Stanford, Bedfordshire

Stanford is a hamlet in the English county of Bedfordshire. It is part of the that also contains the villages of Southill, Broom and Ireland....

, before meeting the River Ivel

River Ivel

The River Ivel is a river in the east of England. It is a tributary of the River Great Ouse.-Course of the Ivel:The river Ivel rises just north of Baldock in Hertfordshire, but most of its course lies within Bedfordshire. It flows through Stotfold, Arlesey, Henlow, Langford, Biggleswade, Sandy and...

 at Langford

Langford, Bedfordshire

Langford is a village and civil parish situated alongside the River Ivel in the county of Bedfordshire.-Origins:The village is of Saxon origin, first mentioned in 944AD. and at one time it had one or more fording points across the river. The name is based on the words long ford from the length of...

.
Its name is not ancient but a back formation from Flitton.
See http://www.wildlifebcnp.org/localgroups-flitvale.htm for more info on the river

Fishing the River Flit
According to "FishHere" web site "River noted for Carp, Dace, Perch and Roach fishing. Run by Shefford and District Angling Association. Permits are available from local tackle shops."
See http://www.fishhere.co.uk/FishingDirectory/FishingDirectoryCategories/FishingDirectoryViewItem/tabid/146/Default.aspx?IID=2369