David & Frederick Barclay Castle

David and Frederick Barclay are reclusive identical twins who have an estimated net worth of £7.2B. In 1993, the brothers bought the lease of the island of Brecqhou in the British Channel Islands. They've recently built this castle on the island. The castle was designed by Quinlan Terry and features 3 foot thick granite walls, two swimming pools, and a helipad.