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The French-Polish filmmaker surprised Cannes with a short film for the Italian fashion house

Roman Polanski introduced the premiere screening of his collaboration with Italian fashion giants Prada on Monday (22 May) by telling the audience the three-minute film was an "anti-commercial".

In his speech, delivered in French, the director added that he wanted to prove he "can make short films as well as long films." The film, titled A Therapy, was announced as a complete surprise before the screening of his 1979 film Tess, which was showing as part of the Cannes Classics section.

At odds with the majority of fashion shorts, Polanski's film is heavy in dialogue.

A suave, melodramatic Helena Bonham Carter, draped in a fabulous purple fur coat, swans into the office of Ben Kingsley, who plays her silent psychoanalyst.

She removes the coat, kicks off her Prada shoes, drapes across a chaise lounge and recounts a dream surrounding typically Polanski themes of loneliness and anxiety.

Kingsley drifts off, besotted with Bonham Carter's coat, which hangs on a hat rack. He approaches it, caressing the fur with personable affection before slowly putting it on and fully embracing his fantasy. "I'm a very lonely person," Bonham-Carter says, "I think it's because I'm rich, and daddy left me everything."

At the end the message reads "Prada Suits Everyone," while Bonham-Carter asks: "What does it all mean?"

The notion of a "fashion film" has grown in recent years; Prada have previously worked with Jordan and Ridley Scott, and in 2010 Dior hired David Lynch and Missoni hired Kenneth Anger to shoot their 2010 A/W selection.

Though its characters are self-indulgent fantasists, Polanski's film is witty, sharp, stylish and wonderfully camp. As a brand/artist match, it's near perfect. As Polanski says, "It's very refreshing to know that there are still places open to irony and wit and, for sure, Prada is one of them."

• Watch Polanski's A Therapy here.

Foraging experts make careful calculations but plants and fungi never appear on cue. John Wright explains his seasonal struggle to predict the weather

"Sorry," I said, "they are completely out of season". I should have known better. It was late April and a TV director was after some truffles for a programme he was making. It would have been nice to oblige but it was like being asked for snowdrops in August or swallows in December. A week later a friend popped round and showed me 20 of the damn things he had found in his garden.

In my line of work this sort of thing happens all the time and it is difficult to account for – biology is messy and organisms seem determined to confound our expectations. One of the most agonisingly difficult things I have undertaken was to write a forager's calendar for my River Cottage Hedgerow Handbook. I checked my records, the date stamp on a thousand photographs, spoke to friends and canvassed opinions. The very next year, 2010, spring was extremely late and bulrushes appeared at least three weeks after I said they would and elderflowers two weeks. In my Mushroom Handbook I say unequivocally that wood blewits appear in late autumn, but they can pop up in June if they feel like it.

Perched as we are between the westerly winds from an ocean and easterly winds from a continent it could be cynically said that we have no climate in the UK, just weather, and it is of course mostly weather that determines when things grow. On the whole plants are reasonably well behaved and appear within a week or three of when they are expected, but sometimes, like a magnificent crop of redcurrants I once found in November, they grow at completely the "wrong" time.

Fungi are the worst offenders, steadfastly refusing to follow the rules I have so helpfully laid down for them. The warm, dry March this year was followed by a cool and spectacularly wet April. This may have fooled the truffles into "thinking" it was autumn and time to make an appearance. There are indeed quite a few mushrooms around at the moment which we would not expect to find until October – I have seen wood blewits, oyster, horse and field mushrooms, and Pholiota adiposa (a large, slimy toadstool) for example.

In a mild winter, mushrooms can still be found in January and February and, with the possible exception of March, some mushroom seasons can continue all year. This odd behaviour is almost entirely down to rain. If it rains you will likely get mushrooms, though you will get many more if it is autumn rain. I have a long history of making bad predictions about the coming mushroom season for the simple reason that all I am doing is trying to predict the weather, something that not even the Met Office is very good at.

The flowering plants are a little fussier about when they leaf, flower and fruit because there is little point in doing the first two if winter is about to arrive. However, while the main flush for dandelions is late April, in most years enough flowers can be found for a dandelion wine right up until late September. Similarly, June is when nearly all the elderflowers appear but the picture in my hedgerow book was taken in a decidedly unseasonal October! Nettles, too, have their season – March and April – but a fine crop can often be gathered in early winter.

The influence of people can be seen at work here – most of these plants have been cut back and flower or grow again. The most noticeable human effect is in the micro-climates found in towns and cities. These can raise average temperatures by two or three degrees. For example the elder in my mate's London garden last year had finished flowering by the beginning of June, a month earlier than we saw in Dorset.

Have we seen a change in the seasons and a corresponding change in plant and fungi activity? Yes, certainly, though the effect is largely drowned by year to year variation; nevertheless the Woodland Trust tells us that in spring plants come into leaf and flower around a week earlier than the 40 year average of 1961-2001. This is a remarkable effect considering that the central England temperature record shows only a fraction of a degree Celsius increase over that period, but this may be because the temperature increase is more pronounced in the spring and plants are very sensitive to temperature.

A paper analysing historical records published in 2000 by Sparks et al, showed a remarkably neat correlation between flowering date and temperature. Elderflowers, for example, flower six days earlier for ever degree warmer it is, on average, in April. Other plants show a greater or smaller effect. This is the dark science of phenology – linking biological activity to climate.

People ask me if mushrooms have reacted to a change in climate and I always tell them no – it is just the weather.

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The Norwegian mass murderer meditated to numb his emotions. The effect of any practice depends on our values

Meditation makes you calmer and clearer and encourages empathy and kindness … right? Not if you are Anders Behring Breivik who has told psychiatrists that he used meditation to "numb the full spectrum of human emotion – happiness to sorrow, despair, hopelessness, and fear". He still practises it behind bars to deaden the impact of his actions.

Breivik uses meditation as a form of mind control – a way to focus the mind and exclude responses that get in his way. You could argue that he is meditating wrongly, but I think his testimony shows that the effect of any practice, meditation included, depends on the ends to which it is recruited. Breivik's aims were determined by his racist beliefs and meditation didn't challenge them.

We've been here before. Breivik likened himself to a Japanese banzai warrior seeking satori – Japanese Zen enlightenment – to harden his heart. Samurai, inspired by Zen teachings, often used meditation to develop their skills and overcome fear of death. Zen's long association with the samurai bushido ethos culminated, after the Meiji restoration of 1868, in the support of virtually the whole Zen establishment for the military expansion that culminated in the second world war. Japanese Buddhists rejoiced that the Pearl Harbor attacks had occurred on 8 December, the day when they mark the Buddha's enlightenment; and leaders insisted that fighting was a patriotic and a Buddhist duty.

Established religions commonly support a nation's war effort, but the Zen enthusiasm for Japanese militarism strayed so far from the Buddha's nonviolent teachings that it raises more fundamental questions. After the war a group of Japanese Zen scholar-priests (the Critical Buddhism school) investigated how their branch of a seemingly pacifist tradition had ended up affirming war. They concluded that Zen's reinterpretations of early Buddhism had obscured its fundamental tenets.

The first Buddhist precept is not killing living beings. As the Buddha says: "All men tremble at punishment, all men fear death; remembering that you are like them, do not kill" (Dhammapada 119). But Mahayana Buddhism, from which Zen evolved, teaches that all phenomena are mysterious and ungraspable – empty of any fixed essence. So what should we relate to everyday reality in which, the Buddha stressed, actions have consequences and ethical considerations apply? The various Mahayana schools have different answers, but Zen teaches that the ultimate perspective should inform everything.

That elevates a non-dual state of mind over ethical distinctions. The 17th-century master Takuan told his samurai students: "The uplifted sword has no will of its own, it is all of emptiness. The man who is about to be struck down is also of emptiness, and so is the one who wields the sword." Later, the self-sacrifice of kamikaze pilots was hailed as an expression of enlightenment.

Westerners learned of Zen's tarnished history through Brian Victoria's Zen at War (1997), but few western Zen practitioners have seriously re-evaluated their tradition. Many like Zen's anti-intellectualism, feeling that doctrines and ethical precepts smack of rigidity, dogma and rules. But the Buddha made right understanding the first item in his eightfold path because he knew that everyone is guided by a worldview and underlying beliefs. His teachings seek to reshape those views so they eliminate attachment and support liberation. Ultimately, that includes attachment to doctrines, but discarding them too soon means that pre-existing beliefs and prevailing opinion go unchallenged.

Zen's non-dual philosophy obscured Buddhism's ethical teachings; Breivik used meditation to serve the murderous objectives of his racist ideology. Meditation, or any other practice, is just a technique. Its effects, for good or ill, depend on the system of values that guide how a person uses it.

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