He was born in the parish of Saint Michael, Barbados on 19 October 1749, the son of John Piggott of Grenada, and trained for the law at the Middle Temple, being called to the Bar in 1777.
He began his legal career in Grenada, where he was appointed Attorney-General, returning to England in 1783, where after building up a practice as a common lawyer, he moved to the court of Chancery.
He was Solicitor-General to the Prince of Wales from 1783 to 1792, when he was discharged because of his membership of the Society of the Friends of the People, a radical reform group.
[1] Under the Whig administration of 1806, he was selected to be Attorney-General, was knighted by the king and given a safe parliamentary seat by the Duke of Norfolk at Steyning.
Although he did not appear in court, he was involved in the 1812 trial of William Booth for forgery, in his role as "constant Counsel for the Bank of England".