St Mary Undercroft
The Chapel of St Mary Undercroft is a Church of England chapel in the Houses of Parliament.
It had been a crypt below St Stephen's Chapel and had fallen into disuse. After a fire had destroyed St Stephen's Chapel it returned to its former use as a place of worship. It is still used for this purpose today. In particular, children of peers, who possess the title of "The Honourable", have the privilege of being able to use it as a wedding venue. In addition, members of parliament and peers have the right to use the chapel as a place of christening.
It is a Royal Peculiar chapel - meaning that it is not the responsibility of a diocesan bishop. The building is administered through the Lord Great Chamberlain and Black Rod and it has no dedicated clergy: by convention services were conducted by the Rector of St Margaret's, Westminster, a member of the Chapter of Westminster Abbey. In 2010 the Speaker of the House of Commons used his right of appointment to nominate an outsider, Revd. Rose Hudson-Wilkin as the Speaker's Chaplain.
The body of Margaret Thatcher was kept in St Mary Undercroft on the night before her funeral on 17 April 2013.