The first Unitarian service was preached by Theophilus Lindsey on 17 April 1774. Supported by Joseph Priestley, Richard Price (see scientific life assurance) and others he used space recently vacated by an auction house, a simple hall built on the site of the old Essex House. Benjamin Franklin was also present at this service. The congregation grew and Lindsey's friends funded a purpose-built chapel on the same site, opened on 29 March 1778.
By the 1880s another Unitarian congregation had grown in Kensington but without a chapel. Also two Unitarian bodies required better offices: the British and Foreign Unitarian Association and The Sunday School Association. It was decided that the Essex Street congregation would join that in Kensington, in a new church (funded by Sir James Clarke Lawrence and his brother Edwin) and the old chapel would be redeveloped to become Essex Hall, the headquarters of British Unitarianism. With substantial funding from Frederick Nettlefold this was built in 1886, destroyed in WW2 but rebuilt and, 2012, is still the Headquarters of the General Assembly of Unitarian and Free Christian Churches.
The picture source website is excellent for the history of the building.
