Passengers on the train that derailed and slid down an embankment in Cumbria said they felt bumps and violent swaying as the crash happened.
Ms Thomson said the train lurched from side to side before derailing
Ruth Colton told BBC News 24 that it felt like the Virgin London to Glasgow service was being battered by heavy winds before her carriage flipped.
BBC executive Caroline Thomson said her carriage "lurched very, very badly from side to side" before turning over.
Ms Thomson said it "did a sort of bump" before swaying "very dramatically".
Ms Thomson, chief operating officer for the BBC, said: "It did a sort of bump and then one felt it beginning to move slightly and for a minute you thought it would sort of right itself.
"For a minute I thought don't worry this is fine. You knew it was something a bit more serious than normal.
"But you thought it's just gone a bit fast or something and it's fine and it will sort itself and then the swaying became very dramatic... you suddenly thought 'crikey it's off the track'.
"And there was a moment where it turned on its side when you thought - you know - 'am I going to be very seriously hurt here?'"
Ms Thompson said that as she was helped off the train, she could see "lots and lots" of walking wounded.
Ms Colton said some of the carriages were stuck up in the air and some were lying on their sides.
"We all had to climb out the top of one of ours," she said.
Ms Colton described the moments before the crash: "I was just reading a book and it started to get really bumpy, like we were being battered by heavy winds or something, and then suddenly the carriage flipped over.
"The train seems to have fallen down an embankment..."
Another passenger, Catherine Haig, said: "The train started to sway side to side and I thought this doesn't feel right.
"You could feel the brakes skidding and then it really went side to side - and lights were flickering.
"The drinks cart kind of flew... forward and then we were on our sides. And it happened so quickly that you didn't have time to think what happened."
Passengers being treated at a farm near the crash site also described how the train began to rock and jolt as if violent braking was taking place.
They reported a blinding flash as the train left the track, believed to have been caused when overhead cables were broken.
Laptops and other luggage flew through the air as carriages toppled, they said.