I heard last night of the death of Brian Sewell which is not wholly unexpected as Max Hastings gave him a valedictory dinner at the National Gallery in 2001 at which Sewell apparently gave brilliant impromptu responses to the paintings.   I remember the moment when he emerged as a public figure defending Anthony Blunt from a telephone box in his etiolated voice.   As a critic of historical exhibitions, he could be impressive.   The first exhibition he reviewed that I was associated with was of Master Drawings from the National Portrait Gallery.   He took the trouble to compare the English with the American catalogue and lambasted us for omitting some of the drawings from the London showing.   But as a critic of twentieth century art he was unnecessarily and tiresomely negative.