• A Southern passenger train derailed close to Lewes railway station in East Sussex at around 3.54pm this afternoon.
• The three rear carriages came off the tracks and turned onto their sides, trapping around 40 people.
• Two people were seriously injured, while nine sustained less serious injuries.
• Emergency services descended onto the scene, stretchering off casualties and guiding passengers down the tracks.
• Southern has advised passengers not to travel through the area, with major disruption expected until around 10pm.
• The final passengers were rescued from the train and evacuated by a fleet of three air ambulances at around 6pm.
• Images appear to show a section of buckled track behind the overturned carriages – though there has been no official confirmation of the cause.

British Transport Police (BTP) has declared a major incident following the derailment this afternoon.

In a statment, BTP said: ‘A major incident has been declared after three carriages of the train derailed onto their side, leaving a number of people trapped. They have now been safely evacuated.

‘At this time we believe that two people have sustained serious injuries and a further nine patients have sustained less serious injuries. Patients have been assessed and treated at the scene, with some transported to local hospitals.’

‘Officers are continuing to respond at the scene alongside colleagues from Sussex Police and the local Fire and Rescue and Ambulance Services.’

Assistant Chief Constable Ian Drummond-Smith said: ‘We’ve declared a major incident and a significant emergency service response is ongoing at the scene, but all passengers on the train have now been safely evacuated from the service.

‘Our thoughts are of course with everyone affected, and I’d like to reassure the public that we’re supporting the Rail Accident Investigation Branch to establish exactly what’s happened. We’ll provide further information as soon as we are able.’

Josh Babarinde, MP for Eastbourne, where the train was due to terminate, said he has been informed that one of his constituents suffered a broken rib in the derailment.

In a social media post, Mr Babarinde described the incident as ‘utterly shocking’, and thanked the emergency services for their efforts.

He wrote: ‘I’m full of gratitude for our emergency services who have responded quickly and are pulling out every stop to ensure that passengers and staff who were on the train are taken to safety as soon as possible – thank you to them,” he wrote.

‘This is clearly distressing for those passengers and staff on board, even if they didn’t sustain physical injuries, and I have made representations for the appropriate mental health support to be made available to affected passengers and staff without delay.’

He added that there would be serious questions to answer about how the accident unfolded, but called for unity in the immediate aftermath.

Passengers Rob Bradley, who was travelling with his six-year-old daughter Mabel, described scenes onboard as ‘pandemonium’.

Mr Bradley told BBC News: ‘It was quite pandemonium for a while. There’s hundreds of police, fire and ambulance crews and everything.’

He said that passengers were trapped onboard for ‘about an hour and a half’ after the accident.

Mr Bradley said it was ‘incredibly hot’ because the air conditioning had stopped working, and the windows and doors remained closed.

South East Coast Ambulance Service has said there were about 150 people on board the train when it derailed near Lewes.

A spokesperson said: ‘We can confirm that two patients have sustained serious injuries and a further nine patients have sustained less serious injuries.

‘Patients have been assessed and treated at the scene, with some transported to local hospitals for further treatment and care.

‘A number of passengers who did not require hospital treatment have been taken to a local community centre, where they are being supported by partner agencies.’

It added that it continues to respond to the major incident alongside other emergency services and urged people to avoid the area.

South East Coast Ambulance has confirmed that ‘two people sustained serious injuries’.

The train from London Victoria to Eastbourne derailed when it was between Haywards Heath and Lewes stations.

Norman Baker, who is a former Lewes MP and an ex-transport minister, suggested the derailment may have been caused by a section of the track buckling in the heat.

He told Times Radio: ‘They’ll want to make sure that the railways are completely safe before any trains are allowed back on them and if it has been the case — that the rails have buckled — that will take considerably longer to repair.

He said Southern Rail did not need to suspend all services through Lewes, as it has done, because the train between Brighton and Eastbourne does not go ‘anywhere near’ the scene of the accident.

Baker added: ‘No doubt the rail accident investigation board will determine the cause of the accident and take any necessary steps subsequently.’

Today broke the record for the warmest day of the year, with a provisional temperature of 38.1C being recorded in Kew, London.

East Sussex Fire and Rescue Service says it has sent ten fire engines, a command support unit, technical rescue teams, officers and other resources.

A spokesperson said: ‘We have been helping reach passengers and assisting other emergency services.’