The witching hour is almost upon us. And no, we don't mean Christmas, we mean the 'Harry Potter' reunion special.

Double, bubble, toil and trouble... the 'Harry Potter 20th Anniversary: Return To Hogwarts' reunion has been given its second official trailer. This will be the first time the majority of the cast will reunite since the final movie 'Deathly Hallows Pt. 2' in 2011.

The HBO Max production will see the majority of the cast and crew involved in the making of the eight films return back to Hogwarts for an unscripted special. The first film, 'Harry Potter And The Philosopher's Stone' was released in November 2001.

Earlier this month, we saw the first official looks at the upcoming reunion. First, we were gifted with a teaser trailer that showed some of the former HP alums receiving the invitations to the special event; while the first image released last week showed Daniel Radcliffe, Emma Watson and Rupert Grint together in the Gryffindor common room.

Here's the official full-length trailer for the 'Harry Potter 20th Anniversary: Return To Hogwarts' special.

Last week, 'The Late Show With Stephen Colbert' published a parody video about the reunion, with The Sorting Hat of all things/people being the one spilling all of the exclusive behind-the-scenes secrets.

Harry Potter 20th Anniversary: Return to Hogwarts' will air on New Year’s Day exclusively on Sky and streaming service NOW in Ireland and the UK.

Sky Cinema and NOW Cinema have all ten of the films from the franchise available to view this December. The 'Harry Potter: Hogwarts Tournament of Houses' quiz show, hosted by Helen Mirren, can be streamed from December 29.