Lego started in Denmark in the 1930s as a small family business making wooden toys. It's now the most profitable toy maker in the world. But with great success comes great stress, with Lego staff under huge pressure to think bigger and better, especially in the run up to Christmas. Lego's Big Christmas goes behind the scenes as the world's biggest Lego store prepares to open in London's Leicester Square. The one-off film also follows Duncan, Britain's only certified Lego professional, who is attempting to build the largest Lego model ever - a giant Tower Bridge, using nearly six million bricks. There's also Sophie and Michael, two adult fans of Lego, who unashamedly maintain their love for the brick. There's also Lego designer Justin, whose first kit - a re-imagining of The Beatles' Yellow Submarine - prepares to hit the shelves.