Anne McMeehan, a director of the Association for Unit Trusts and Investment Funds (AUTIF), accepts that dress is important in the financial services world, particularly in the conservative cloisters of the City, but argues that it is easy to send the wrong message.
"I was at an investment management conference on a ship where I met a fellow who wore a T-shirt and shorts, when everyone else was wearing casual clothes. His justification was that as he was a millionaire, he could dress as he wanted."
McMeehan concludes that while being a millionaire made this man a success in his own terms, he was hardly dressing for future success by being at odds with everyone else he was trying to do business with.
McMeehan, who favours classic business suits and darker colours, says the dress-for-success code is simple: "One dresses not for oneself, but for one's audience. You have to give people what they expect."
What people expect and the fervour with which they hold to their expectations varies within the City of London from sub-culture to sub-culture. Arguably the fiercest, most unreconstructed of the City of London cultures is to be found in the foreign exchange, bond and swap dealing rooms in the City.
Here, the way a male or female colleague dresses is held up to the closest scrutiny. Any deviation from the norm is reviled and ridiculed.
"It's dark suits - black, grey or blue - and a smart label for the men who want to impress. Armani, Ted Baker, or whatever, is fine," says the head of a fixed interest dealing room at the London office of a leading Canadian bank.
"The women have a little more latitude when it comes to blouses or shirts - but that's because of the way these places are: they're animal houses, and what the girlies wear doesn't matter that much," he adds.
Chris Macdonald, managing director of Brooks Macdonald Gayer, a leading independent financial adviser which won four awards last year, agrees that there is a uniform, but that appropriate dress varies from sector to sector.
"If I see someone at the sharp-end of technology or design and they're wearing a suit and tie, then I'd probably judge them to be out of touch. If I happened to be going into the City of London to see an investment manager, I'd expect that type of dress and would want to know why someone was out of uniform."
As an independent financial adviser with a website to develop, a large number of private clients to deal with, and fund managers to visit, Macdonald finds himself adopting different garb to suit the occasion.
"Apart from City of London visits, formal attire is essential for dealing with private clients," he says. Macdonald adds that the code is fairly straightforward. Dark suit, quality shirt and tie, and cufflinks are what is expected.
"There is room for manoeuvre. You can express your individuality within certain well-defined limits. For example, it's OK to wear an extravagantly designed tie if the rest of the uniform is conservative, but you've got to watch out for cufflinks, which can be gimmicky. Gimmicks imply spiviness - cufflinks with pound notes on are wide boy gear."
Width in the pinstripe of a suit is to be applauded, says Macdonald: "The wider the better, up to a maximum of two inches." Wide check patterns on shirts, however, are decidedly out. The rule of thumb here is the wider the check, the wider the individual.
Other minutiae of the dress-for-success code include a moratorium on braces. Says a British investment banker working for a US investment bank in London: "They are dead and buried. They send completely the wrong message, namely 'I used to work in the 1980s, but haven't done anything since'."
And one of the oldest maxims in the City still applies for banks, lawyers, accountants, and just about anyone male hoping to be taken seriously in financial services: the only thing that looks good in brown is 5lb of potatoes.
Simon Harrison, a partner in international headhunting firm Hedirick & Struggles, specialises in financial services. He accepts the argument that dress can and should be modified to suit an interview.
For example, he would never dress down for an interview with a City lawyer, and would be more casual if meeting people from a financial services dot-com organisation, who tend to dress more Silicon Valley than City of London.
However, even when meeting warriors of the new economy, Harrison tends to favour a shirt and tie because of personal preference, which he feels is important.
"You can't dress entirely for your audience. You've got to be yourself. If the person you're meeting doesn't like you, it really doesn't matter what kind of clothes you wear," he says.
Many of the US investment banks in London have taken to wearing casual clothes on "dress-down" Fridays. But the need for a uniform again is evident. Shorts and T-shirts are out. Chinos and casual sweaters and shirts - the Ellesse and (still) Ralph Lauren look - are de rigeur.
However, the financial services world is a conservative place and there is a growing feeling that casual dress is bad for business. Noone would go on the record to voice this sentiment but one industry observer summed it up well:
"People are increasingly coming to think that casual dress can lead to casual behaviour in the office. Sloppiness, if you will. I think you'll see a move back to wearing suits all week. If that helps promote profile and an image of success, then the trend will become a rigid rule again."
There you have it. Profile and image of success lie at the heart of dressing appropriately. The rule seems to be: if in doubt, take the conservative option.