Dr Belvedere is a non-canonical character who was created for the film adaptation of Wasps' Nest in Series 3 of ITV's Agatha Christie's Poirot. He is a specialist doctor with a clinic on Devonshire Street, London. John Harrison, who has a terminal illness, is one of his patients. Dr Belvedere's specialisation is not known.
Dr Belvedere is portrayed as somewhat of a mystery man for much of the episode. He is seen on several occasions with a walking stick which had a skull on the tip. No one knows who he ws until Japp bumped into him in a hospital.
He did break his silence by telling Harrison's fiancée Molly Deane about Harrison's illness and short time, because he believed it would be in his patient's own interest. Later when Poirot seeks him out, he tells him as well.
Dr Belvedere is played by John Boswall. This character does not occur in the the original story. John Harrison does consult a specialist in Harley Street (not Devonshire Street) but his name is not given.