Train disruption is set to continue until midday in Cambridgeshire, with cancellations and delays seen across the Great Northern and Thameslink networks.
The disruption follows a record-breaking heatwave in the United Kingdom, with temperatures reaching 40 degrees centigrade in some areas.
As part of these cancellations, no Thameslink trains will be running north of London, until midday today (Wednesday, July 20).
This includes all Thameslink trains to or from Cambridge and Ely.
A large number of Great Northern services have also been cancelled.
A spokesperson from Thameslink railway said: "Due to a number of incidents across the Great Northern and Thameslink network, train services running across these networks will be cancelled, delayed or revised.
"Disruption is expected until approximately 12.00 (midday) today, Wednesday July 20.
"You cannot travel on much of the Thameslink and Great Northern network this morning.
"Please delay your journey, or travel at a later date...
"...This follows on from the extreme weather we experienced on Monday (July 18) and Tuesday (July 19)."
Those planning on travelling on the East Coast Main Line, between Peterborough and Kings Cross, have also been urged to plan ahead following fire damage.
A spokesperson from Network Rail said: "Teams from Network Rail need to carry out repair and recovery work after a fire spread onto the railway line in Sandy, Bedfordshire, which is on the route between Peterborough and (London) King’s Cross.
"The incident has caused major damage to signalling equipment and a level crossing in the area, both of which need complex repairs to be completed."
National Rail Enquiries' Journey Planner can be used to help plan and check rail routes.
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