Six people were being treated in hospital last night and a driver was being questioned by police after a National Express coach overturned on a motorway.
The single-decker coach clipped a kerb, hit a lamppost and a tree and toppled over onto the driver's side as it entered Newport Pagnell services on the southbound M1.
Police were called by service station managers just after 4pm. Four ambulances went to the scene. Thirty people were injured and the six with serious injuries were taken to hospitals in Milton Keynes, Northampton and Oxford.
Emergency services said 11 people, described as "walking wounded", received minor injuries and 17 were discharged at the scene.
The driver, who had to be cut free from the wreckage, was breath tested at the scene and arrested shortly afterwards on suspicion of drink-driving and dangerous driving.
A casualty bureau, for those who are concerned a relative or friend was on board, has been opened. The numbers are as follows: 0800 056 0146 or from outside the UK +44 20 7158 0198.
The M1 is still running smoothly, though there is no access to the services itself and investigators hope to remove the coach from the slip road during the night.
The bus left Birmingham Digbeth at 2pm bound for Stansted and Luton Airport. It stopped at Birmingham International at 2.20pm and Coventry at 2.40pm and was due to arrive in Stansted Airport in Essex at 5.55pm. One of the passengers said the coach was "going fast round corners" before the crash.
Kirsty Plummer, from Luton, told Sky News: "I knew something was going to happen, the driver was swerving so I put my seat belt on."
She said other passengers who did not fasten their seat belts fell on top of her as the coach overturned and were more seriously injured.
Eddie Gershon, a spokesman for Welcome Break, which operates the service station, said: "The coach went over on its side after hitting a lamppost and a tree, I've been told, and ended up in the car park. "About a dozen staff from Newport Pagnell came out and gave initial first aid before the emergency services arrived."
A spokeswoman for Thames Valley Police said: "It appears that shortly after 4pm the National Express coach clipped a kerb and rolled on to its side."
Superintendent Mick Doyle told Sky News the driver was breath tested at the scene and found to be over the legal limit for driving.Reuse content