Putting up the Christmas tree is a big enough task but rarely do you need a cherrypicker, forklift and 1200 hours to do so.

Sydney shoppers stepping into Pitt St Mall will not miss the jaw-dropping giant Lego Christmas tree, which was lit up at 8pm on Thursday.

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More than 500,000 Lego bricks have been used to construct the 10m-tall tree.

Weighing in at 3.5 tonnes, the tree is adorned with basketball-size baubles and accompanied by a scruffy surfer Santa Claus figure who watches over the tree.

Chief Lego builder Ryan McNaught said the public’s reaction to the tree has been fantastic.

“I was just watching this businessman hurrying along – he glanced at it, took two more steps and then just stopped,” he said.

“If we’ve got the power to stop your classic businessman I can only imagine what that can do for an eight-year-old kid.”