Rail passengers in London faced chaos on Wednesday as the disruption from mass cancellations caused by the heatwave spilled into a second day.
The route between King’s Cross and Peterborough was closed until the early afternoon, with a reduced service running later in the day.
Avanti West Coast said services from London Euston were cancelled due to ongoing repair work following damage caused by fires in the Hatch End area of north-west London on Tuesday.
A spokesman said: "Train services are severely disrupted across our network as a result of damage to the overhead wires at multiple locations due to yesterday's extreme heat. Network Rail is still at the sites carrying out repairs.
"Customers should make sure they check their journey before leaving for the station, and train tickets for yesterday and today will be valid for travel tomorrow. We're sorry for the inconvenience this will cause."
Pictures showed huge crowds of passengers at Euston waiting around the station's information board on Wednesday afternoon for an update on their trip.
Nicole Dixon, 26, missed her uncle’s funeral in Carlisle after any available trains from Euston were cancelled.
“I’m incredibly annoyed, frustrated and a bit exhausted,” the private PA said.
“I was told that there was an unlikely chance of getting a train out (yesterday) but that (today) they would 100% be running. I explained to (staff) that I needed to be home for a funeral in the morning.
“I’ve felt really annoyed this morning as I was assured I’d be able to make it to the funeral.”
The London Euston station Twitter account said the station "was getting very busy as we recover from the impact of yesterday’s heat".
They warned passengers it is "essential that you check before you travel to the station, as your train may be delayed or cancelled".
Network Rail said passenger numbers on Tuesday were around 40 per cent lower than the same day last week.
As temperatures climbed above 40C for the first time ever in the UK on Tuesday, major fire incidents were declared in London, Norfolk, Suffolk, Lincolnshire, Leicestershire and South Yorkshire amid the tinder-dry conditions.
Sadiq Khan said the London Fire Brigade (LFB) had received more than 2,600 calls throughout the day – seven times the usual number.