National Highways has now cleared Skanska to start main construction before the end of year on the 16km dual carriageway upgrade in Cambridgeshire and Bedfordshire.
The extra cash will compensate for cost inflation impacts caused by climate campaign group Transport Action Network’s legal challenge to planning consent.
The scheme running between the A1 Black Cat roundabout in Bedfordshire to the A428 Caxton Gibbet in Cambridgeshire is now due to open in 2027.
A number of junction improvements will be made, including a new three-tier junction at the Black Cat roundabout allowing free flowing traffic onto the A1 and the new carriageway.
The scheme will deliver significant benefits by preventing delays and increasing capacity along the route.
It will also contribute to unlocking the potential for longer term economic growth in the wider Oxford-Milton Keynes-Cambridge areas which have been identified by the Government as a key national priority.