I was fortunate enough to be one of those 100 students who were used as extras when Harry Potter 4 were filming at the Glenfinnan Viaduct.

The scene was of the Hogwarts Express going over the famous Viaduct on its way to Hogwarts (the same one which was featured in Chamber of Secrets when the Ford Anglia had its run-in with the train). We all had to arrive at Glenfinnan Station really early at 5:30 in the morning.

They were using a helicopter to film the train going over the Viaduct. We were given strict instruction not to look out the window at it and to just pretend it wasn't there.

Unfortunately Dan [Radcliffe], Rupert [Grint] and Emma [Watson] weren't there. Instead, they had three doubles, the Harry double said that his name was Ryan, the Ron double's name was Ricky. Hermione double's name was Jo and she was like 24 but she still looked like Emma. They said that they were staying in a hotel in nearby Fort William and that Dan, Rupert and Emma were filming a different scene down in London. At 1 p.m. We had to swap with 50 more extras because we were only allowed to work so many hours as we were under 16 and came in so early in the morning. I managed to get some pictures of the train on my phone and tried to get some of the doubles but was told we can't have pictures of them.