HM Haji Hassanal Bolkiah Mu’izzaddin Waddaulah has been the Sultan of Brunei since 1967. Following the death of Thai King Bhumibol Adulyadej in 2016, the Sultan is the wealthiest monarch in the world. His official residence has over 1,800 rooms and he maintains a car collection in the thousands. He owns many properties (via the Brunei Investment Authority) in the UK including the famous Dorchester Hotel. He is estimated to be worth $20 billion.