UPGRADE work has started on a flood defence system, the failure of which led to York’s Boxing Day floods.

The £13 million upgrade of the city’s Foss barrier and pumping station has begun even before planning permission has been granted.

But Environment Agency chiefs say they still don't know why the control room - meant to be watertight - was inundated by floodwaters on Boxing Day, forcing them to raise the barrier.

Homes and businesses along the course of the Foss and its tributaries were flooded after the defences were overwhelmed by the sheer volume of water coming down the river.

The pumping station was designed to be able to pump about 30 tonnes of water per second from the Foss into the Ouse and it was unable to deal with an estimated 35 tonnes per second that evening.

The upgrade, which will include the installation of eight more powerful replacement pumps, is set to increase its capacity so it can handle at least 40 tonnes per second.