Johnny Depp paid a surprise visit to a school in London this morning in response to a fan letter from one of the students.  Beatrice Delap, eight years old, sent Depp a letter stating that she and her fellow students were having a hard time at Meridian Primary School of Greenwich in their attempt to have a mutiny against their teachers.  The actor is currently filming "Pirates of the Caribbean: On Stranger Tides" in nearby Old Naval College, a picturesque 17th century seafaring center, so he grabbed four other cast members and dropped by the school in full costume as Captain Jack Sparrow.  Both students and teachers were delighted to host the actors, and the children serenaded Depp with pirate-themed songs they wrote.  Meridian teachers say they encourage their students to write to people and invite them to visit since it makes education more fun and introduces the kids to the power of writing and communication.