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.

The huge and gorgeous Titian, The Vendramin Family, c.1540-c.1560, displays a frieze of males of all ages, three or four generations – and an adorable lap dog held close by the youngest boy – in marvellously sumptuous costume. The painting is surrounded with portraits by an ardent admirer of Titian's, Anthony van Dyck, our interest in the Titian deepened by the fact that Van Dyck once owned it. It is but one of the stars of this fascinating sampling of the collecting habits of artists themselves.

Here comes the Switch House. The 10-story new build attached to the Gilbert Scott Bankside power station that was the first instalment of Tate Modern in 2000 opened to the public this weekend. Tate Modern’s expansion became almost a necessity as the original estimate of two million annual visitors became five million.

As if to signal a coming of age, this year's Whitstable Biennale has a theme: The Faraway Nearby. And so for the first time artists have a guiding idea with which to post-rationalise their work. Until now, the 10-day festival of visual art has staked out broad territory with performance, film and emerging talent. So perhaps an equally broad theme was needed to ensure that works comprised of fan letters, a lecture tour in a car park and a new flavour of ice cream could cohere as a successful biennale.