William Mainwaring was, the MP for Middlesex

Middlesex (UK Parliament constituency)

Middlesex is a former United Kingdom Parliamentary constituency. It was a constituency of the House of Commons of the Parliament of England then of the Parliament of Great Britain from 1707 to 1800 and of the Parliament of the United Kingdom from 1801 to 1885....

 from 1784 and chairman of the Middlesex and Westminster Quarter Sessions for a similar period.

In the 1802 General election

United Kingdom general election, 1802

The United Kingdom general election, 1802 was the election to the 2nd Parliament of the United Kingdom. It was the first to be held after the formation of the United Kingdom of Great Britain and Ireland...

, he was opposed by the radical Francis Burdett. Mainwaring had previously resisted Burdett's calls for an inquiry into prison abuses, particularly at Coldbath Fields Prison

Coldbath Fields Prison

Coldbath Fields Prison was a prison in the Mount Pleasant area of Clerkenwell, London. Founded during the reign of James I , the prison was completely rebuilt in 1794 and extended in 1850. It was used to house prisoners on short sentences of up to two years...

. Mainwaring was defeated by Burdett but the election was declared void in 1804 and in the following contest William's son George Boulton Mainwaring

George Boulton Mainwaring

George Boulton Mainwaring was a Tory MP for Middlesex, a position that had also been held by his father William Mainwaring.Mainwaring is thought to have been born in 1773. He was the son of William Mainwaring....

was elected. The result was reversed in favour of Burdett in 1805 and the back in favour of Mainwaring Junior in 1806. Mainwaring did not contest the 1807 election and Burdett was not elected.