It is sobering to think that the medieval and Renaissance paintings that fill our galleries represent just a fraction of the artistic output of that period. Panel paintings – not to mention exquisitely fragile wall paintings – have for the most part succumbed to the ravages of time, and those not destroyed by fire or flood, acts of war or vandalism, or abortive attempts at restoration have simply faded, darkened or discoloured.

A gorgeous white horse with flowing mane, poised and alert in a rocky landscape next to a watchful lion, is an extraordinary study of suppressed tension. A wistful North American moose, a herd animal living on its own on the Duke of Richmond’s estate; a monkey about to eat a crab apple – these are some of the subjects depicted by that artist of genius, the Liverpudlian George Stubbs (1724-1806).

American photographer William Eggleston is famous for dedicating himself to colour photography at a time when it was still considered kitsch – acceptable for wedding and Christening photos, but not much else. The best known example of his embrace of colour is a 1973 photo of a red light bulb hanging from a red ceiling, a picture devoid of subject matter beyond redness and the associations it triggers.

Winifred Knights (1899-1947) was an impeccable draughtsman: her portrait drawings are compelling. She deployed fine webs of lines, her sure hand applying gradated pressure resulting in mesmerising studies of people that are hypnotically fascinating. Who knew pencil could do so much? But she was also a painter, a slow worker using techniques that were deliberately old-fashioned.

A neon sign over the Barbican’s Silk Street entrance reads Scandinavian Pain. Following its victory over us in Euro 16, it seems that Iceland is now drenching us with its special brand of melancholy. Things are not that simple, of course. In his work, Icelandic artist Ragnar Kjartansson indulges his penchant for sorrow with such bitter sweetness that, with many a gentle sigh, emotional pain morphs into something more akin to pleasure.

This programme was not ironic, humorous or in any way lighthearted. I’m fairly sure of that, but worry that perhaps I’ve missed the joke.  A withering take-down or a meaty exposé of the corruption and excess of the extremely wealthy would have served a purpose, but this was neither. It pretended to offer a salacious glimpse behind closed doors but instead delivered a congratulatory slap on the back to the villains we love to hate – it seemed, in fact, to be a straightforward “Banker’s Guide to the Art Market”.

Nous avons Brexité but we are still welcome at the 47th Rencontres d'Arles. Each summer this beautiful French town gives itself over to an international photography festival which this year features around 40 exhibitions of varying sizes with countless lectures, parties, book signings and fringe events.

It's 100 years since Georgia O’Keeffe first showed at Alfred Stieglitz’s 291 Gallery in New York, a hub of avant-garde activity, and the opening room of this major retrospective revisits the 1916 exhibition. Inspired by Arthur Dow’s emphasis on freedom of expression and Wassily Kandinsky’s book The Art of Spiritual Harmony, O’Keeffe made a series of drawings and paintings in which natural forms are abstracted to the point where they are only just recognisable.

Just a few hours earlier, as helicopters clattered overhead and thousands joined the good-humoured but impassioned March for Europe, an evening of contemporary art felt like the last thing anyone needed. On this day of all days, launching an art festival inspired by the success of Nuit Blanche in Paris felt like an unnecessary application of salt to the wound.

The opening image of this new David Hockney exhibition – a sketchily painted portrait of a seated man, slumping heavily forward, his head buried in his hands – could be a portrait of Brexit despair.