When this moved to St James' Place in the New Town, members on the Southside petitioned to form a new congregation, which was created as the Third Relief Church in 1803.

The Scotsman expressed surprise that this innovation had taken place in one of the dissenting churches, "which are generally understood to be more austere than the Establishment".

[5] They continued as an independent congregation until 1833 when they successfully petitioned the General Assembly of the Church of Scotland to join their denomination, albeit on the condition that the organ be removed.

They were joined by the Relief congregation from Roxburgh Terrace Church and worshipped jointly at the Lancastrian School on Davie Street.

[10] Prominent ministers included Alexander Topp, who later became moderator of the General Assembly of the Presbyterian Church in Canada, and Walter Chalmers Smith, who wrote the hymn "Immortal, Invisible, God Only Wise".

A mission chapel (known as the House of Mercy) opened at High School Yards, Infirmary Street at the southern edge of the Old Town on 26 July 1868.

In 1981, it was restored for use as a lecture theatre by the Royal College of Surgeons of Edinburgh with funding from King Khalid of Saudi Arabia.

In his honour, it was given the full title: King Khalid bin Abdul Aziz of Saudi Arabia Symposium Hall.

As the college's commercial operations began to grow, the building was again renovated in 2005 to increase the auditorium's capacity.

[20] John Kinross altered the building at its conversion to an Episcopal church and a reredos by Hamilton More Nisbett for the Lady Chapel was added in 1902.

[18] Charles McKean called the interior as a "magical vertical space", citing its exposed stone walls and wooden ceiling.