The Warner Bros. Studio Tour - The Making of Harry Potter, at the Hertfordshire Leavesden Studios, gave a preview of its expansion on 3 March. It showcased a major new addition - Platform 9 3/4 with the original Hogwarts Express train, steaming on a set of tracks.

The iconic 78-year-old red steam engine (named 'Olton Hall') was used in the movie franchise to transport Harry, Hermione, Ron, and the rest of the gang to Hogwarts school.

The train carries a special significance, according to Mark Williams, who played Ron's father, Arthur Weasley, who was at the studios for the preview.

"It's very important, the Hogwarts Express. Firstly it was the beginning of every adventure. And also it is the point at which the muggle and wizard worlds intersect. It's only a thin wall between outside and inside and so it was very magical," he said.

He went on to explain what visitors can expect from the set expansion: "You can walk down and look at the compartments which are all dressed as if on a set and then obviously there's a locomotive to look at, and then there's a special section over there where you can sit in compartments and behind you the journey's projected and you can take part in that."

The windows will show iconic train scenes from the movie including Harry's first Chocolate Frog and the Dementor attack. A selection of prop luggage will also be on show.

The new 20,000sq ft section of the exhibition will open to the public on 19 March.