A passenger on the train that derailed in East Sussex has described how people and gadgets sailed through the air after a 'violent jolt', before passengers broke out 'screaming'.Twenty people were hospitalised after the Southern Rail train carrying 150 people came off the tracks near Lewes station just before 4pm on Thursday, including two with 'severe' injuries.The rear three carriages were thrown onto their sides after apparently hitting a section of badly buckled track, leaving around 40 passengers trapped inside.Teddy Birkbeck, 18, boarded the train from London Victoria at Gatwick Airport after flying back from a lads' holiday in Albufeira, Portugal, with his cousin and friend.He said the train had already been delayed in its journey to the airport, with officials explaining over the intercom that it was 'due to the heat'.Mr Birkbeck, a farmer from Sussex, told the Daily Mail: 'It felt like there was something wrong from the start. There were two sudden jolts soon after we left Gatwick. My mate even joked, "That hurt!"'Then it was all smooth going - until we got near Lewes.'The trio were among eight people travelling in the rear carriage, which ultimately careered furthest down the bank. Teddy Birkbeck, 18 (centre), with his cousin Charlie Hobden (left) and their friend were making their way home from a lads' holiday in Albufeira, Portugal Mr Birkbeck described people and gadgets sailing through the air The rear three carriages overturned and fell off the rail track Images appeared to show a section of badly buckled track just behind the train, with experts suggesting this may have happened due to the extreme heat Mr Birkbeck was watching TikToks on his phone, nursing a 'slight hangover' from the holiday, when he felt a 'violent jolt'. He said: 'The train suddenly started to lean from side to side, and things were floating around the carriage in slow motion, like we were in space.'I saw my mate's laptop go through the air, and a bottle of water as well. Then we slammed down on our side.'I screwed my eyes shut, but it felt like we were in a car that was drifting after the brakes had been slammed on. I thought to myself: "I am going to be seriously hurt here."'We were sitting on the left of the carriage, so it wasn't too bad in the end, but people on the right flew from their seats and fell down onto our side.'Everyone was silent for about 30 seconds - though it felt like an hour - and then people started screaming. Some were really panicking. It was difficult to know which way was up or down.'I had smacked my head on something, and saw that some people were bleeding.'Charlie Hobden, Mr Birkbeck's cousin, said it felt like they were 'in a washing machine' when the carriage tumbled over onto the embankment. The rear carriage, in which Mr Birkbeck and his friends were travelling, skidded furthest down the embankment Some passengers were able to clamber through the emergency doors onto the sides of the overturned carriages Mr Birkbeck's view from the track after being helped out of the carriage by emergency workersImages from the scene show that the rear carriage slid around ten metres down the slope to the left of the track, bulldozing trees and coming to rest in the adjacent field.Three of the carriages whipped over, while the front five remained upright. Behind the stricken rear carriage could be seen a section of track that looked to have buckled severely, with several sharp swerves along it. James MacCleary, the Lewes MP, said concerns had been raised about the condition of tracks in the area due to the sustained heatwaves.He told Times Radio: 'I had a meeting literally last week with [Greater Thameslink Railway], who are the parent company of Southern Rail, and we did discuss the track and the fact that it has been a bit bumpier in recent months, which is possibly a result of the incredibly hot weather we’ve had recently.'A temperature of 38.1C was recorded at Kew Gardens in west London on Thursday, making it officially the hottest day of the year.Mr Birkbeck continued: 'Another passenger eventually managed to get the emergency exit open so people could climb out on top, but we decided to stay inside because it was actually cooler to begin with.'There were also a couple of elderly ladies who were distressed, so we wanted to stay and help them.'I had to force the door into the driver's compartment at the back of the carriage to get the first aid kit.'South East Coast Ambulance Service said around 150 people were on board the train, and 20 were injured. It said two people were rushed to the major trauma centre with 'severe' injuries, while a further 18 patients were also in hospital. Three air ambulances and at least 20 other emergency vehicles raced to the scene, while a number of passengers who did not require hospital treatment were taken to a local community centre to be triaged and supported.