The contractor will spend five years building the 5km scheme, with construction due to start in 2027.

The Environment Agency project will carve out a new stream and wetland corridor to the west of Oxford city centre, running from north of Botley Road to Kennington before rejoining the River Thames.

Work will include lowering parts of the floodplain and building new flood walls, embankments, culverts, bridges and flood gates.

The new channel will take excess flow from the Seacourt, Bulstake and Hinksey streams during floods, cutting water levels through the city.

The scheme will protect homes and businesses as well as the railway, local roads and key utilities.

Over its lifetime, the project is expected to save more than £1.8bn in flood damage and disruption.

Graham will also create more than 20 hectares of new wetland habitat and around 16 hectares of floodplain meadow.

Towles Mill weir on the Seacourt Stream will be removed, opening up fish movement through Oxford’s waterways for the first time in more than a century.

Graham contracts director Alastair Lewis said: “This is an extremely important project, given Oxford has lived with the threat of serious flooding for generations.

“The vital piece of infrastructure will tackle the flood risk directly in a way that works with the landscape rather than against it.”