Portrait of William Petyt, Keeper of the Tower Records

Petyt, a lawyer, political writer and advocate for the power of Parliament, was made Keeper of the Records in 1689. This was the office responsible for looking after early state records, which were housed at the time in the Tower of London, before the establishment of the Public Record Office in 1838.

Van Bleeck, a Dutch portrait painter, has shown Petyt, beneath his family's coat-of-arms, holding a rolled copy of the 'Magna Carta', the ancient royal charter agreed by King John in 1215. Lawyers like Petyt argued that the 'Magna Carta' was a legal ratification of an English constitution that protected freedoms and by extension the power of Parliament.