Gary Sandford, 67, of Letchworth, is found guilty of causing serious injury by dangerous driving.
Bedfordshire Police says the road is likely to remain closed for hours.
The water company said it operated the storm overflow following prolonged wet weather.
Police confirm a man, 43, died and say his family is being supported by specialist officers.
Officers say the vehicle is connected to nationwide raids at charity clothes banks.
A man in his 20s suffers serious injuries in the crash in Letchworth.
Network Rail says major disruption is expected until the end of the day.
The two men were arrested after a long-running investigation into organised thefts of high value cars.
Georgia Nixon and Stacey Almond are among those turning a nose for a bargain into a business.
