Philip Hensher: It's a performance just to enter the UK

For centuries, the life of the arts has depended on the occasional shot in the arm delivered by glamorous visitors. When Handel, Mozart or Haydn turned up in London in the 18th century, the result was a huge new public audience for music. Pissarro's paintings of Upper Norwood, Monet's views of the Thames and Kurt Schwitter's last years in Ambleside are significant moments in English art. In recent years, the net has spread further. Writers, performers, musicians, film-makers, painters, sculptors, and architects from outside Europe have enriched our national life beyond measure.

Since 2008, immigration for workers from outside the EU has operated on a points-based system. Under this system, introduced by the Labour government, workers may be admitted according to their value to the economy. In a first-rate example of the Game of Unexpected Consequences, large numbers of creative artists were caught in a net intended for temporary workers.

If you wanted to perform or work in the UK, and expected to be paid for your efforts, you now needed to apply as if you were intending to migrate. Other points-based systems had recognised that the pianist Lang Lang, say, was in a different category to temporary workers in industry, and left creative artists out of the system altogether. That was not a solution which appealed to the systematic mind of the immigration system. Distinguished foreign pianists would either have to apply for an "entertainer visa", which generally applies only to those appearing in major, Government-sponsored festivals and those willing to appear without a fee. Otherwise, they would have to queue up with everyone else.

Needless to say, these rules are far more stringent than anything applying to sportsmen and women, who may be paid and who may bring a technical or support team of any size with them. A succession of sports-worshipping governments could never permit even the most piddling of Japanese tennis players to be held up for a moment at immigration on their way to Court 15 at Wimbledon. But an artist, a musician, a writer, a film-maker – well, who cares about them, really?

A celebrated case quickly followed the change of rules. For some time, English National Opera has been improving its international standing by using a wider pool of directors, from non-traditional backgrounds, than in the past. In 2009, it obtained the services of the great Iranian film director Abbas Kiarostami for a production of Così fan Tutte. Kiarostami is a giant, and his presence in one of London's opera houses ought to have been comparable to the Royal Opera House getting a production of Boris Godunov out of Tarkovsky in 1983.

The immigration services made Kiarostami apply twice for a visa, demanding his fingerprints on two separate occasions. The film director withdrew his application and never came to Britain, to our loss. The Così was a sad, muted affair. There are many similar stories. Photographers, ludicrously, have been forbidden to take photographs while in the country. I wonder whether novelists, visiting festivals for no fee, are similarly warned that they may not do any work on their fiction while in the country. Are artists who carry paintbrushes under threat of interrogation? Certainly, there have been cases of musicians with instruments being refused entry, even when there was no likelihood of them playing for payment.

Of course, the very grand names are mostly likely to get through, though their treatment may make them think twice about coming back. But how did those very grand names ascend to that eminence? Through the free exchange of ideas, and the opportunity to travel through the world in a professional capacity. These points have been made this week in an open letter to the Home Secretary by a long list of writers, and they really seem to be unanswerable.

In recent days, the Chinese authorities have released the artist Ai Weiwei from an unjust captivity. They did so because his work is widely known in the West, and, in part, because the people in Britain who know and love his work from direct encounters with him protested so vociferously.

There are other Chinese artists have not travelled to Britain, and have not been able to convey their message through their work. Pissarro was welcome here as a refugee. But these days, it sometimes seems as if the British immigration authorities are happily doing the work of oppressive foreign governments.

Plenty of administrations would be delighted if their awkward artists were refused temporary visas by many more governments. But our national life depends, in large part, on the presence of foreign, independent-thinking minds.

Star of a final sad drama of BBC error

I always loved the actress Margaret Tyzack, who died this week. She had a marvellous presence and splendid deportment, often compared to a galleon in full sail; an unmistakeable voice, which could fill the theatre; and the most expressive face imaginable. She was one of those actresses who transcended any category. I suppose old-fashioned people would have called her a character actress, but, from the 1967 BBC Forsyte Saga onwards, she was much easier to fall in love with than many a soubrette. Everyone who knew her says she was a very nice woman, and modest with it. A year or two back, we found some DVDs of the ancient BBC I, Claudius, and found ourselves utterly gripped, above all, by Tyzack's intense, tragic Antonia. This eminence didn't protect her, however, from a shameful and deplorable blunder by the BBC. Announcing her death, the BBC television news used a photograph of her colleague on I, Claudius, Siâ* Phillips, still very much with us – a memorable Juliet in Bristol last year. Human error, the BBC said. We know the mischief that can work, but all the same – how can two so very different actresses be confused by a whole team of people? More to the point, is that any kind of way to pay respect to someone who, in the days before BBC drama was reduced to police procedurals and Great Expectations for the ninth time, helped give it a worldwide reputation?

Magical Magyars get the picture

Strangely enough, before going to see the Royal Academy's Hungarian photography show, it had only vaguely occurred to me that most of its central names were Hungarian at all. Everyone knows these photographers – Brassaï, Kertész, Robert Capa, Moholy-Nagy – or at the very least, you know their images. Capa's militiaman, caught just as he is killed, falling backwards; Brassaï's lovers in a Paris café; Kertész's poised fork; it is hard to imagine the history of photography or reportage without many of these images. Because they only started from the same point, however, and because they scattered all over the globe, I suspect many casual members of the photography audience hardly group these photographers together. And yet, seen in bulk, they have a wonderful coherence. They are tied together by a clear thread. These days, the capturing of the moment, the street photograph and the image have spread and spread, and become almost meaningless in their variety. An austere and exhilarating aesthetic links the news photography of the Great War with Kertész's magical late photograph 'Martinique', with its liminal sensuality and withdrawn suggestion. To discover this is to rediscover the power and poetry of photography itself.

arts@independent.co.uk