The AA said it recovered 100 vehicles from flood water, mostly across Surrey and Essex, following torrential overnight rain.
Darron Burness, head of the AA's flood rescue team, said: "It's gone a bit mad today with a massive surge in flood call-outs following the heavy overnight rain.
"Some of the people we went out to this morning got stuck after their cars were swamped by passing lorries. If you risk driving into flood water, you're a sitting duck as the air intake on most cars is pretty low, which makes them very vulnerable.
"Rather than taking a detour, these drivers will be making a rather embarrassing call to their insurer this morning and many will have their pride and joy written off. As well as swamping cars, the bow waves of passing vehicles can flood property too, forcing water into people's homes."
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A number of families were on board the service from London Euston to Stoke. One family left the train early to escape the abuse.
She's called Amy, and was visiting a hospital.
The victim is believed to be aged in his 60s and though next of kin have been informed, formal identification has not yet taken place.