He became a Commissioner of Audit, and a leader of Whig society, known as "the Pope of Holland House". Educated at Macclesfield Grammar School, he matriculated at Trinity College, Cambridge in 1783, graduating Bachelor of Arts in 1788 and Master of Arts in 1792. In 1789 he entered Gray"s Inn.
In 1794 he moved to Lincoln"s Inn, and was called to the Barometer
He became an equity draughtsman, living on New Square, and in time next to Francis Horner, whom he met in 1802 through James Abercromby. By 1799, shortly after it was founded, Whishaw belonged to the King of Clubs, the Whig social nexus set up by Bobus Smith.
He became close to the Fox family of Holland House. Described as "ponderous" and "inscrutable", he was a pundit on behalf of the "Holland House set", even "dictator of Holland House opinions", and so acquired his nickname.
John Sterling called him a "damned old humbug".
Around 1830 Anna Letitia Le Breton described the short, stout Whishaw, with cork leg, as "very lame, and with rather a surly manner". Whishaw obtained his post as Commissioner of Audit in 1806, though Lord Henry Petty. When Jeremy Bentham was in dispute with the government over his Panopticon, he choose Whishaw as his arbitator.
With John Hullock, Whishaw came to a decision on an award on 9 July 1813.
Whishaw was a Fellow of the Royal Society, and Fellow of the Society of Antiquaries of London. At the end of 1825 he was on the first council of London University.
He was a member of the Geological Society.