John Wallop, 3rd Earl of Portsmouth

John Charles Wallop, 3rd Earl of Portsmouth (18 December 1767 – 14 July 1853), styled Viscount Lymington until 1797, was a British nobleman and lunatic.

When, in 1808, she found herself no longer able to control the Earl, her relative, Dr. John Combe, was added to the household, to help suppress Portsmouth's manias.

When Newton attempted to have Portsmouth declared insane that autumn, Byron's affidavit as to the circumstances of the marriage was instrumental in getting the charge dismissed.

[2] However, the new Countess was by no means equal to the task of controlling Portsmouth; his behaviour grew more erratic, while Mary Anne carried on an adulterous affair with William Alder, who fathered three children with her.

[4] A new commission de lunatico inquirendo took place in 1823, at the instigation of Portsmouth's nephew Henry Wallop Fellowes, and it was revealed that the Earl had been badly mistreated by his new wife and her lover, who had spat on him and beaten him.