Robley is perhaps most well known for his eccentric collection.
The Maori mummified the tattooed heads of their tribesmen and Robley decided to acquire as many as possible. Over the years he built a collection of 35. In 1908 he offered them to the New Zealand Government for £1,000 but his offer was denied. Today, 30 of his heads are in the collection of the Natural History Museum in New York.