After the clearance, development progressed slowly. The National Gallery was built on the north side between 1832 and 1838 to a design by William Wilkins, and in 1837 the Treasury approved Wilkins' plan for the laying out of the square, but it was not put into effect. In April 1840, following Wilkins' death, new plans by Charles Barry were accepted, and construction started within weeks. For Barry, as for Wilkins, a major consideration was increasing the visual impact of the National Gallery, which had been widely criticised for its lack of grandeur. He dealt with the complex sloping site by excavating the main area to the level of the footway between Cockspur Street and the Strand, and constructing a high balustraded terrace with a roadway on the north side, and steps at each end leading to the main level. Wilkins had proposed a similar solution with a central flight of steps. Plinths were provided for sculpture and pedestals for lighting. All the stonework was of Aberdeen granite.