The strange tomb was erected by acclaimed landscape gardener and prolific horticultural author John Claudius Loudon (1783-1843) to the memory of his parents William (d. 1810) and Agnes (died 1841.)

darkestlondon.com/2012/02/20/loudons-floating-coffin

londonist.com/london/secret/london-s-most-peculiar-grave-the-floating-coffin-of-pinner