It's an odd thing with Christ Church. The July streets of Oxford were swarming with tourists while the quads and Gallery were near-deserted, hardly surprising since the porters at the gate did their level best to prevent me from getting in, claiming the Gallery is closed on Tuesdays (not in July and August it's not).

That glitch over - and their attitude an unwelcome contrast to that of the charming gallery staff - one passes a display of wall cards marking the Gallery's 250th anniversary of the extraordinary General Guise Bequest to Christ Church of 1765. Each card bears the thoughts of a visitor on art and museums. These range from a hope that the General's coffin is wide enough to enable him to revolve within it (a complaint about the Government's arts budget policy), to a comparison made with the gift from Viscount Fitzwilliam in 1816 to Cambridge University, to more than one person claiming that appreciation of the arts is the principal distinguishing mark of human vis a vis animals. These claimants belong seemingly to the Harvard cognitive evolution school that tends to believe that our cognitive abilities differ from those of other animals in kind, as opposed to the Darwinians, who incline to a difference merely in degree.

On to the 33 drawings of the Undisputed Masterpieces show, works of the Italian and a few of the N. European Renaissance; and it's a pity that one of the latter, a Hugo van der Goes study of Rachel and Jacob from Genesis, is placed so that it's hard to view. These works are practice studies either in their own right, or as preliminary models for a subsequent, more elaborate work, or as a cartoon (a full-sized drawing for a planned painting or fresco that was pricked with fine holes for the more precise transfer of drawing to canvas or church wall).

For me there were three highlights in a scintillating display of technical bravura by these masters of Florence, Venice and Greater Flanders, the latter in part represented by some post-Hieronymus Bosch allegorical witchcraft studies. Bust of a Man in black chalk and wash by Giovanni Bellini (1430 - 1516): a tough man, pleased with himself, taking for granted the desire of the artist to draw his likeness, perhaps mirroring the self-confidence of the thrusting city-state of Venice. These qualities bring to mind the famous portrait of Doge Leonardo Loredan in the National Gallery by the same artist. Head of a Young Woman in dark and light chalk by Andrea del Verrochio (c. 1435 - 1488) where the complexion of the face set against hair and a trailing ribbon is a marvel of delicate shading. Finally, a cartoon believed by General Guise to be by Leonardo himself - and with excellent reason - though attributed today to the second tier Milanese artist Giampetrino (c. 1500 - c. 1545). This study of the Virgin contemplating the infant Jesus as she looks forward to those events that were to conclude his life bears a subject that could not be more common in Western art. But here the depiction by the simplest means of tender love mingled with dread is of the rarest beauty.