UBS  has just a “few general rules” for its dress policy: “There are no flip-flops, no shorts, and shirts have to have collars. We are not exactly dress-down, but we are more relaxed than many City [of London] institutions. People don't have to wear suits and have freedom within pretty obvious guidelines. If you are meeting clients, you dress appropriately,” explains a spokesman at the Swiss investment bank.

As the mercury heads north, the thoughts of many in the business community turn to packed, pressure-cooker trains, shirts stuck to backs, constricting ties and just how broadly they can interpret the phrase “smart casual”.

Shorts at work remain a no-no in almost any part of the white-collar economy. The good news, though, is that companies even in traditionally buttoned-up sectors are embracing a kind of smart-casual liberation.

In adland, it seems, there is little in the way of formal rules. “We don't have a dress policy at all,” says Farah Ramzan Golant, chief executive of the UK advertising agency Abbott Mead Vickers BBDO. “People are allowed to express their identity through what they wear. We wouldn't want to start dictating skirt lengths, as some law firms do.”

However, she notes, there are unspoken rules: “The main thing is to look sensible in front of clients. I would not expect people to wear shorts or flip-flops but I would never inspect what people are wearing. Everyone is a brand and every brand expresses itself visually, but it is less about being correct and more about being communicative.”

This attitude is to be welcomed, says Brendan Barber, general secretary of the UK's Trades Union Congress: “When the weather is hot, staff need to stay cool and sensible employers understand that it makes sense to allow employees to dress down for summer.”

Mr Barber adds that while he is not advocating bikinis and bare chests, “allowing employees to discard their tights, ties and jackets will avoid them feeling faint from the heat at their desks and allow staff to carry on working productively ... a cool smart-casual approach is needed”.

Cary Cooper, a professor at Lancaster University Management School, takes a similar line. “If you're not client-facing in offices, I do not see why you cannot wear smart casual – you can always take a tie along and put it on if you need it. We should lighten up in the office.”

Yet he adds there is still a certain image that goes with business – whatever they wear, staff should feel as if they are at work. And this, Ms Ramzan Golant says, is why she frowns on shorts – not because she dislikes them, but because of the message they send out. “Shorts signal that you are off duty, that you are on holiday. That is why they belong on the beach and not in the workplace.”

Dress also varies with sector. Business casual still has some way to go in politics and the law: when was the last time you saw a male member of parliament in the UK House of Commons without a tie?

In the technology sector, policies are more relaxed. While a spokeswoman at Bebo, the social networking site, rules out beachwear, “smart tailored shorts would work,” she says. And visitors to MySpace's London office on a summer's afternoon will encounter anything from maxi-dresses and dungarees to the latest Manolo Blahniks.

Perhaps the greatest shift in office attire, however, has been in financial services. Once a buttoned-up industry, its change in attitudes is now apparent, from the open-necked hedge fund managers of Mayfair to the big banks. “If you walk around the City, you will see people looking smart, but shirt and jacket smart, not shirt and tie,” Prof Cooper says.

While business casual is a surprisingly broad church, at its limits would be Agent Provocateur, a British lingerie company. Sarah Schotton, senior designer, describes the policy as “business sexy”: “We're supposed to dress smartly and sexily – like the brand – so that means high heels, make-up and dressing up, and no jeans and no trainers.”

Would Agent Provocateur countenance shorts if the weather got hot enough? According to Ms Schotton: “Well, I suppose you might get away with a pair of sexy hotpants – but only if your bottom was up to it.”

瑞銀(UBS)在著裝方面只有“一些總體規定”，這家瑞士投行的一位發言人解釋道：“不能穿夾趾拖鞋，不能穿短褲，襯衣必須有領子。我們并未真正實行便裝(dress-down)，但比倫敦金融城(City)許多其它金融機構要寬松的多。大家不必穿套裝，而且在很明顯的指導方針范圍內有自由度。如果你要見客戶，就應該穿適當的服裝。”

隨著氣溫不斷升高，許多商界人士的念頭開始轉向擁擠、如高壓鍋般悶熱的地鐵，汗濕后緊貼后背的襯衫，緊束的領帶，以及“雅致便服”(smart casual)這個短語的意思究竟能有多寬泛。

幾乎在白領階層的所有領域，工作時穿短褲依然是個禁忌。但好消息是，甚至那些屬于傳統上著裝保守行業的企業也開始接受某種雅致便服的解放。

在廣告界，似乎沒有任何正式規定。“我們沒有任何著裝要求，”英國廣告公司Abbott Mead Vickers BBDO首席執行官芙拉•拉姆贊•戈蘭(Farah Ramzan Golant)表示。“大家可以通過衣著展示自己的個性。我們不愿意像某些律師事務所那樣，開始規定裙子的長度。”

然而，她指出，還是有一些不言自明的規則：“重點是在客戶面前要顯得有頭腦。我估計不會有人穿短褲或夾趾拖鞋，但我也決不會去檢查大家的衣著。每個人都是一個品牌，每個品牌都從視覺上展示自己。不過關鍵不在于著裝是否正確，而是著裝是否能傳達出某種信息。”

英國職工大會(Trade Union Congress)秘書長布倫丹•巴伯(Brendan Barber)表示，這種態度將會受到歡迎。“天氣炎熱的時候，員工需要保持涼爽，而明智的雇主會認識到：允許員工在夏天穿得隨意一些是有道理的。”

巴伯補充稱，雖然他不提倡比基尼或坦胸露背，“允許員工脫下緊身襯衣、領帶和外套能避免他們因炎熱在辦公桌前感覺暈眩，使員工有效開展工作……涼爽的雅致便服著裝方式是必要的”。

蘭開斯特大學管理學院(Lancaster University Management School)教授卡里•庫珀(Cary Cooper)表達了類似的觀點。“如果你在辦公室里不用面對客戶，我看不出為什么你不能穿雅致便服——你可以隨身攜帶一條領帶，如果需要的話就戴上。在辦公室我們應該放松點。”

不過他補充道，仍然需要某種與工作相匹配的形象——不管他們穿什么，員工應該感覺到自己是在工作。拉姆贊•戈蘭表示，這就是為什么她會對短褲皺眉頭——不是因為她討厭短褲，而是因為短褲所傳達出的信號。“穿短褲意味著你下班了，你在度假。因此它們適合海灘，而不是工作場所。”

著裝還因行業而異。商務便裝(business casual)要想被政界和法律界所接受仍需假以時日：你上次見到英國國會下議院的男性議員不戴領帶是什么時候？