The approved plan was revised in the next few months. In a letter dated 5 August 1811 Soane informed the client of a revised estimate reducing it from £11,800 to £11,270. The College was still falling short of funds. However, on 19 September 1811 Margaret Desenfans wrote to Soane offering a further £4,000, which brought the total fund above budget. She wrote that it was ‘the only consolation [she] can find in this life will be to see the wishes and intentions of her dear friend Sir Francis Bourgeois carried out in the most compleat (sic) and expeditious manner’. It was not until 11 October 1811 that the college gave Soane permission to go ahead with the building work and the foundations were laid on 19 October 1811.

The delay of three months between the approval of the design and the start of construction allowed time for some revisions to the plan that, for example, introduced the arcade on the east front as a series of unadorned arches as well as alternative designs for the Mausoleum exterior.

At the last minute the Warden decided the new Gallery should be located further from the College and it was moved five feet away.