Billy meets Mina and Allan at the ruins of Greyfriars.
William "Billy" Bunter was a obese student of Greyfriars School and was a fellow classmate of Harold Wharton, Robert Kim Cherry, and John Night. His sister Bessie was married to Wharton, who became the future dictator of Britain.
History
As of 1958, William still reside in Greyfriars School - which had long been closed down - as an old man and the school's caretaker, and sells information about the former students of the school. During the "Big Brother" years, William escaped persecution by the Ingsoc government probably due to his sister's influence and Wharton's past sympathies to his former schoolmate.
Billy encountered Wilhelmina Murray and Allan Quatermain, in which he told them of Greyfriars having been a recruiting ground for spies and agents for the crown since the 16th century and Robert Kim Cherry's new identity of Harry Lime, the head of MI5. After Murray and Quatermain left, William informed them to Harry Lime.
Source material
Billy Bunter was a schoolboy created by Charles Hamilton and appeared in stories set at Greyfriars School. Due to the character still under copyright, Billy Bunter is only refer by his first name.