In Five Go to Billycock Hill (the 16th book in the series), the Famous Five—Julian, Dick, Anne, George, and Timmy the dog—head off on a camping holiday during the Whitsun term break.They set up their tents on Billycock Hill, a scenic spot near a bustling Royal Air Force (RAF) airfield. There, they befriend a local boy named Toby, who frequently visits his cousin Jeff, a brilliant and celebrated flight lieutenant stationed at the nearby airbase.