Panorama's research for the Queen Camilla programme took it to Westminster and to the Public Records Office.

During the course of the making of the programme, reporter Steve Bradshaw unearthed several documents about the Royal Marriages Act of 1772 and the constitutional problems it has posed.

Here are some extracts from some of the key documents which were found in the Public Records Office.

This letter was a legal opinion on the 1936 Abdication Crisis from Treasury Solicitor to Prime Minister Baldwin. It confirmed the status of the wife of the King as the Queen, adding "His issue can only be changed by legislation."

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This Whitehall memo from 1956 suggests the Royal Marriages Act would be difficult to reform.

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This document was a briefing for ministers in 1955 in response to potential questions about the Royal Marriages Act.

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This secret advice from the Lord Chancellor's office in 1953 confirms the Queen must act on advice from the Prime Minister.

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This Home Office memo from 1941 about the Royal Marriage Act deals with the question of the Royal Family marrying only in Church of England ceremonies.

All documents courtesy of the Public Records Office