The first significant alteration made to the building was the single, long gallery added by Sir James Pennethorne in 1860–61.
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".

With the demolition of the workhouse, however, Barry was able to build the Gallery's first sequence of grand architectural spaces, from 1872 to 1876.
Built to a polychrome Neo-Renaissance design, the Barry Rooms were arranged on a Greek cross-plan around a huge central octagon.
Though it compensated for the underwhelming architecture of the Wilkins building, Barry's new wing was disliked by Gallery staff, who considered its monumental aspect to be in conflict with its function as exhibition space.
Also, the decorative programme of the rooms did not take their intended contents into account; the ceiling of the 15th- and 16th-century Italian gallery, for instance, was inscribed with the names of British artists of the 19th century.
However, despite these failures, the Barry Rooms provided the Gallery with a strong axial groundplan; this was to be followed by all subsequent additions to the Gallery for a century, resulting in a building of clear symmetry.

Pennethorne's gallery was demolished for the next phase of building, a scheme by Sir John Taylor extending northwards of the main entrance.
Its glass-domed entrance vestibule had painted ceiling decorations by the Crace family firm, who had also worked on the Barry Rooms.
A fresco intended for the south wall was never realised, and that space is now taken up by Frederic, Lord Leighton’s painting of Cimabue's Celebrated Madonna carried in Procession through the Streets of Florence (1853–1855), lent by the Royal Collection in the 1990s.
The first significant alteration made to the building was the single, long gallery added by Sir James Pennethorne in 1860–61. 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".
With the demolition of the workhouse, however, Barry was able to build the Gallery's first sequence of grand architectural spaces, from 1872 to 1876. Built to a polychrome Neo-Renaissance design, the Barry Rooms were arranged on a Greek cross-plan around a huge central octagon. Though it compensated for the underwhelming architecture of the Wilkins building, Barry's new wing was disliked by Gallery staff, who considered its monumental aspect to be in conflict with its function as exhibition space. Also, the decorative programme of the rooms did not take their intended contents into account; the ceiling of the 15th- and 16th-century Italian gallery, for instance, was inscribed with the names of British artists of the 19th century. However, despite these failures, the Barry Rooms provided the Gallery with a strong axial groundplan; this was to be followed by all subsequent additions to the Gallery for a century, resulting in a building of clear symmetry.
Pennethorne's gallery was demolished for the next phase of building, a scheme by Sir John Taylor extending northwards of the main entrance. Its glass-domed entrance vestibule had painted ceiling decorations by the Crace family firm, who had also worked on the Barry Rooms. A fresco intended for the south wall was never realised, and that space is now taken up by Frederic, Lord Leighton’s painting of Cimabue's Celebrated Madonna carried in Procession through the Streets of Florence (1853–1855), lent by the Royal Collection in the 1990s.
National Gallery