Warwick Street began its life as a chapel in 1724 when the Portuguese ambassador came to live in Golden Square. Under the Treaty of Utrecht of 1713-14, Catholic ambassadors had the right to have Mass celebrated in their chapels. In 1747 the Bavarian Minister took over the building. This arrangement continued until 1871 when the chapel was transferred to the Diocese of Westminster.
The present church on Warwick Street has its beginnings in the new building designed by Joseph Bonomi the Elder, which replaced the chapel wrecked during the Gordon Riots in 1780. It was opened on 12 March 1790, a year before the Second Catholic Relief Act, on the feast of St Gregory the Great. About twice the size of its predecessor, its facade was deliberately unassuming; its main object was to escape notice as much as possible.
