Going back to some from my own collection here are some images of the British Empire Exhibition which took place at Wembley stadium between 1924 and 1925.
I shall start with the pictures from my collection.
The exhibition featured 3 roller coasters.
The first was a large Scenic Railway type ride without any actual Scenery like many of its contemporaries. Called oddly enough the Gigantic Scenic Railway. The ride like the Margate Scenic Railway Featured 2 side by side lifts but slightly varying layuts on each loop round.
Next door to this ride was the Grand National (also known as the Giant Switchback it seems). This ride doesnt appear to have been a Switchback in the traditional sense but more just a large wooden coaster with a more elongated layout than the nearby Gigantic Scenic Railway.
In a seperate amusement section to the North of the site sat The Racer. A large Scenic Railway coaster that featured two side by side tracks. That as the name suggests raced.
British Pathe has some good footage of this ride running in this video at 13mins 44seconds
Using a couple of images which are not in my collection and I found online I mapped out the locations with a map of the Exhibition. The oddly shaped India Pavillion in the middle there was really handy
Green = The Racer
Red = The Grand National
Blue = The Gigantic Switchback
On a non coaster front you can see a reference in one of those images to the Never Stop Railway. This was a really weird railway design that used rotating tubes with a spiral thread which propelled the train along its course. The thread is variable in its length so when the thread is more compact the train runs slower through stations and then when the thread is stretched out the train runs more quickly. Allowing the train to change speed without changing the speed of rotation of the tubes. Ingenious if not too efficient I imagine.
There is another great video from British Pathe of this running here.