The aftermath of Storm Dennis continued to cause transport chaos on Monday as train lines and roads were blocked by flooding and fallen trees.

Network Rail is assessing the repairs needed to reopen parts of the railway damaged by torrential downpours and strong winds over the weekend.

CrossCountry, Great Western Railway, Northern, South Western Railway, Southern, Thameslink and Transport for Wales were among the operators with delays and cancellations on Monday morning.

No trains could run through Mitcham Junction in south London as the electric third rail was switched off due to flooding.

Rotherham Central station was closed until at least Tuesday due to flooding.

A fault with the signalling system in the Welwyn Garden City area also caused major disruption to services between Stevenage and London King’s Cross.

A Network Rail spokesman said: “Just as with Storm Ciara last weekend, Storm Dennis has had a significant impact on the railway.

“The heavy rainfall, combined with already waterlogged ground conditions, has led to flooding in a number of areas across the network.

“Our engineers have been working in extremely difficult conditions throughout Sunday and overnight to clear the tracks and keep passengers moving.

“The majority of services are now running as scheduled, but we do still urge anyone travelling over the next couple of days to check before they travel at www.nationalrailenquiries.co.uk.”

Surrey Police warned there would be “significant delays into the morning rush-hour” as two out of three lanes of the A3 southbound between the M25 and Ockham were closed due to floodwater from an adjacent field spilling on to the carriageway.

West Mercia Police urged motorists not to drive through flooded roads, warning that water levels are “still high in many areas across Shropshire”.

RAC Breakdown spokesman Rod Dennis said: “Storm Dennis may have passed, but its impacts will be felt by drivers for some time yet.

“Aside from the current road closures, with so many flood warnings still in force there is a very real risk more roads will be affected by flooding over the next few days.

“It’s vital drivers take no risks – if they can’t be sure the water is shallow enough to safely drive through, turning around and finding another route is always the best option.”