The train is made out of 500,000 bricks and includes special effects such as sounds and lighting, meanwhile smoke emits from its funnel.
Three carriages comprise the creation – one houses the engine and driver’s cabin, another is filled with presents, and the third is complete with a Christmas tree.
The train, which is driven by the Christmas Elf, will remain in situ until Sunday (29 November).
This marks the fifth year that Lego has showcased a unique Christmas inspired creation in the capital. It launched the campaign with a 30-metre Lego Christmas tree in 2011, meanwhile other creations have included a giant advent calendar and walk-through snow globe.
Last year, Lego created a Santa’s sleigh with reindeer.