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.”

瑞银(UBS)在着装方面只有“一些总体规定”，这家瑞士投行的一位发言人解释道：“不能穿夹趾拖鞋，不能穿短裤，衬衣必须有领子。我们并未真正实行便装(dress-down)，但比伦敦金融城(City)许多其它金融机构要宽松的多。大家不必穿套装，而且在很明显的指导方针范围内有自由度。如果你要见客户，就应该穿适当的服装。”

随着气温不断升高，许多商界人士的念头开始转向拥挤、如高压锅般闷热的地铁，汗湿后紧贴后背的衬衫，紧束的领带，以及“雅致便服”(smart casual)这个短语的意思究竟能有多宽泛。

几乎在白领阶层的所有领域，工作时穿短裤依然是个禁忌。但好消息是，甚至那些属于传统上着装保守行业的企业也开始接受某种雅致便服的解放。

在广告界，似乎没有任何正式规定。“我们没有任何着装要求，”英国广告公司Abbott Mead Vickers BBDO首席执行官芙拉•拉姆赞•戈兰(Farah Ramzan Golant)表示。“大家可以通过衣着展示自己的个性。我们不愿意像某些律师事务所那样，开始规定裙子的长度。”

然而，她指出，还是有一些不言自明的规则：“重点是在客户面前要显得有头脑。我估计不会有人穿短裤或夹趾拖鞋，但我也决不会去检查大家的衣着。每个人都是一个品牌，每个品牌都从视觉上展示自己。不过关键不在于着装是否正确，而是着装是否能传达出某种信息。”

英国职工大会(Trade Union Congress)秘书长布伦丹•巴伯(Brendan Barber)表示，这种态度将会受到欢迎。“天气炎热的时候，员工需要保持凉爽，而明智的雇主会认识到：允许员工在夏天穿得随意一些是有道理的。”

巴伯补充称，虽然他不提倡比基尼或坦胸露背，“允许员工脱下紧身衬衣、领带和外套能避免他们因炎热在办公桌前感觉晕眩，使员工有效开展工作……凉爽的雅致便服着装方式是必要的”。

兰开斯特大学管理学院(Lancaster University Management School)教授卡里•库珀(Cary Cooper)表达了类似的观点。“如果你在办公室里不用面对客户，我看不出为什么你不能穿雅致便服——你可以随身携带一条领带，如果需要的话就戴上。在办公室我们应该放松点。”

不过他补充道，仍然需要某种与工作相匹配的形象——不管他们穿什么，员工应该感觉到自己是在工作。拉姆赞•戈兰表示，这就是为什么她会对短裤皱眉头——不是因为她讨厌短裤，而是因为短裤所传达出的信号。“穿短裤意味着你下班了，你在度假。因此它们适合海滩，而不是工作场所。”

着装还因行业而异。商务便装(business casual)要想被政界和法律界所接受仍需假以时日：你上次见到英国国会下议院的男性议员不戴领带是什么时候？