London Overground Mildmay Line Collectable Guide
There are 6 collectables near Hampstead Heath (2 fire extinguishers, 2 newspaper stands, 1 route map, and 1 defibrillator)
Collectable #1: Fire Extinguisher
Collectable #2: Newspaper Stand
Collectable #3: Route Map
Collectable #4: Newspaper Stand
Collectable #5: Defibrillator
Collectable #6: Fire Extinguisher