Jude Law, Eddie Redmayne and hundreds of Harry Potter fans descend on King's Cross to mark the departure of the Hogwart's Express from Platform 9 3/4 on "Back to Hogwarts" day.

Various "Potterheads", as fans of the franchise are known, appear dressed in school scarves and carrying wands. They are greeted by an indicator board announcing the steam train's departure from the secret, magical platform.

More than 40,000 people have been sharing tweets using the #BackToHogwarts hashtag.

Both Law and Redmayne will appear in "The Crimes of Grindelwald", the movie sequel to "Fantastic Beasts", set to come out in October this year.