 The first significant alteration made to the building was the single , long gallery added by Sir James Pennethorne in 1860 – 1 . Ornately decorated in comparison with the rooms by Wilkins , it nonetheless worsened the cramped conditions inside the building as it was built over the original entrance hall . Unsurprisingly , several attempts were made either to completely remodel the National Gallery ( as suggested by Sir Charles Barry in 1853 ) , or to move it to more capacious premises in Kensington , where the air was also cleaner . In 1867 Barry 's son Edward Middleton Barry proposed to replace the Wilkins building with a massive classical building with four domes . The scheme was a failure and contemporary critics denounced the exterior as " a strong plagiarism upon St Paul 's Cathedral " . 
