By the late 1780s Sharp was at the hub of the Dissenter movement in London at a crucial period in history when Revolution was in the air and when young intellectual Whigs such as he fell under natural suspicion. (See Richard Price and the Revolution Controversy.) He belonged to the Society for Constitutional Information and helped, with other leading Whigs, to establish the Society of the Friends of the People. At about the same time he became one of the Dissenters' "Deputies" – it being the custom for each dissenting congregation within ten miles of London to be represented by two such deputies and their common aim being to overturn the Test Acts which so discriminated against them. In this latter connection Sharp issued a famous "Letter" in support of repeal.