John Lithgow is in final negotiations to portray Professor Albus Dumbledore in HBO's series adaptation of the hugely popular fantasy books.

The Oscar-nominated star is reportedly "in final talks" to sign up to play the Hogwarts headmaster.

Hollywood has a not-so-mysterious way of casting who they want for roles in films and television shows with major IPs. There is usually a breadcrumb trail that you can trace back to a few previous projects that will help you understand why a choice was made for a particular actor.