He pushed his trolley around and stared at the barrier. It looked very solid.
He started to walk toward it. People jostled him on their way to platforms nine and ten. Harry walked more quickly. He was going to smash right into that barrier and then he'd be in trouble -- leaning forward on his cart, he broke into a heavy run -- the barrier was coming nearer and nearer -- he wouldn't be able to stop -- the cart was out of control -- he was a foot away -- he closed his eyes ready for the crash –
It didn't come...
(Harry Potter and the Sorcerer's Stone)
Ron’s mother told Harry how to get onto his platform – all you have to do is walk straight at the barrier between platforms nine and ten. And he walks and then start running toward the barrier. Now, what does ‘a heavy run’ mean?