John Cosnahan

John Cosnahan (1754–1819) was the first High Bailiff of Douglas, Isle of Man, and Deemster. He was the eldest son of Hugh Cosnahan and Eleanor Finch (1753–1799).

In 1781, as a member of the House of Keys, he was sent to London to speak on behalf of the Island. He spoke so powerfully in the House of Lords on 13 June that year that he helped prevent a Bill proposed by the Duke of Athol to pay extra compensation to the Duke for handing the Island over to the Crown.

In 1808 he became a Water Bailiff or Judge of the Admiralty Court.

In the last few months of his life he was made a Deemster or stipendiary magistrate, although his appointment was delayed by the opposition of the Duke.