Since the National Gallery itself is unlikely to feel able to respond to the attached criticism of its current plans, it is perhaps worth making some comments in defence of them (of course, I am not impartial).
Hewitt is correct that the key is circulation. The system of circulation for most of the National Gallery’s history was a circuit from the original entrance, starting with Italian paintings to the west and ending with nineteenth-century French painting to the east. There was a clear logic relating to national schools, which was a nineteenth-century taxonomy. The clarity of this system of circulation was complicated by the addition of an asymmetric new wing at the back (look at the ground plan) by the Property Services Agency in the 1970s and then further complicated by the addition of the Sainsbury Wing in 1991 which sits slightly separately and at an angle to the original building, as Hewitt correctly points out.
It seems to me that there is a perfectly good architectural and art historical logic to treating the Sainsbury Wing entrance as the main entrance, even if it wasn’t designed to be. It is much larger and more spacious than the original Wilkins Building entrance and more disabled accessible. But to make it the main entrance requires some degree of adaptation of the Sainsbury Wing to accommodate the huge number of visitors. This is what Annabelle Selldorf has been hired to do through a process of international competition.
It creates a more linear route through the collection, starting with fourteenth-century Italy in the west and ending with nineteenth-century France (and coffee) in the east. The changes she has proposed involve some degree of change to the entrance vestibule, giving it more height, putting the cloakroom downstairs, and getting rid of the bookshop which made the Sainsbury Wing entrance a bit cramped.
But there is no change whatsoever to the main floor galleries which have been recently and beautifully restored. So, it looks to me to be pretty – and rightly – respectful of Venturi and Scott Brown’s original, although I know strict conservationists and possibly Denise Scott Brown herself may not agree.