In 1711, parliament passed an "Act for the building of Fifty New Churches in the Cities of London and Westminster or the Suburbs thereof", which established a commission which included Christopher Wren, John Vanbrugh, Thomas Archer and a number of churchmen. The commission appointed Hawksmoor and William Dickinson as its surveyors. As supervising architects they were not necessarily expected to design all the churches themselves. Dickinson left his post in 1713 and was replaced by James Gibbs. Gibbs was removed in 1716 and replaced by John James. James and Hawksmoor remained in office until the commission was wound up in 1733. The declining enthusiasm of the Commission, and the expense of the buildings, meant that only twelve churches were completed, six designed by Hawksmoor, and two by James in collaboration with Hawksmoor. The two collaborations were St Luke Old Street (1727–33) and St John Horsleydown (1727–33), to which Hawksmoor's contribution seems to have been largely confined to the towers with their extraordinary steeples.