When I left home, my mother gave me what seemed to be some odd advice: 'Never trust a man who wears a bow-tie, keeps his money in a purse, or kisses you with his eyes open'.
As it turned out, these were good indicators of exactly the traits to avoid in a man: vanity, meanness, and deceitfulness.
We all form snap judgements about people based on small things like these. Psychologists say we make our mind up about others, consciously or unconsciously, within seconds of their coming through the door.
In this context, clothes are a big giveaway. We all wear them, and they can signal a great deal about us. They can convey personal authority, social standing, religious beliefs and economic status. Clothes can help us convey confidence and competence, or the opposite.
It is a commonplace among those who coach public speaking that an audience's appreciation of a speech is 70% to do with the way speakers look, 20% with the way they sound and only 10% with their content.
Actors understand this; sadly, politicians do not. I have two favourite suits for speaking engagements: one white and one red. Wearing my highest heels with either makes me feel poised and assured.
Uniforms have always been signifiers of status and rank, whether in the army, the church or the law. At the simplest level, if someone walks in wearing a white coat we will assume he or she is a doctor, while large quantities of gold braid on a military-style uniform suggest an African dictator or perhaps a hotel doorman.
Striped grey trousers, a bowler hat and a furled umbrella made up the uniform of the City gentleman until Thatcher's deregulation of the City through the Big Bang in 1986.
With it came a more relaxed transatlantic mode of dress and the introduction of such innovations as dress-down Fridays. This caused great bewilderment among the natives. The Brits don't do casual wear: they confuse it with holiday, sport and gardening wear, and the result tends to be downright scruffy.
David Cameron flaunting his curves on the beach in Cornwall under a Union Jack towel is typical of the British male at leisure. Rugger shirts, baggy jeans and gym shoes are the best they can manage; Mr Bean is their style icon. They understand 'black tie', but when an invitation specifies 'smart casual', they struggle and usually just take off their tie.
We can, of course, be fooled by what people wear. The wolf in sheep's clothing is a powerful image in nursery rhymes and in literature.
There is no doubt that Jimmy Savile's brightly coloured shell suits, fancy dress and mad hair led people to believe that he was a charitable, fun-loving national treasure rather than the serial sex predator we now know him to have been. John McCririck's odd pantomime style of dress meant he was tolerated for years as an amusing eccentric, despite his obvious sexism and misogyny - until Jay Hunt of Channel 4, tiring of his 'offensive' and 'alienating' behaviour, sacked him.
In the boardroom, most men conform to the predictable dark suit, white shirt and discreet club tie. But even here they can get it wrong, for example, the well-known banker (I won't name names) whose shirts were of such cheap, thin fabric that his nipples showed through, or the chairman who thought it appropriate to wear an ancient, stained velvet smoking jacket, made for a much slimmer man, to board dinners.
There is the occasional faux pas such as the matching tie and handkerchief set or oddly patterned shirt, but generally they opt for conventional business attire that does not reveal too much of their personality. The business suit can be regarded as a symbol of orthodoxy, of belonging to the club, and as such provides a protective carapace.
Women, as relative newcomers to the boardroom, have to be sensitive to this, although by the time they get there most have learnt that dressing like a man does not guarantee admission to the club. They usually develop a personal style that is acceptable without sacrificing too much femininity or individuality. We will need a lot more diversity in the boardroom before the dress codes loosen up.
I support a charity called Dress for Success, which provides clothes and accessories, such as shoes and handbags, to women former offenders to enable them to dress appropriately when they go for job interviews and first start working.
Wearing the right clothes is important for their self-esteem and confidence, which is often at rock-bottom when they leave prison. Clothes are no substitute for talent, hard work and perseverance when it comes to finding a job, but they can be a big help.
After a number of years in the fashion industry in my early career, I came to appreciate its importance as a huge and thriving business sector, where creativity and design flourish but also where success depends on an acute understanding of the psychology of clothes.
As Mark Twain said: 'Clothes make the man. Naked people have little or no influence on society.'
Baroness Kingsmill is a non-executive director of various British, European and US boards. Lady Kingsmill can be contacted on firstname.lastname@example.org
Follow her on Twitter: @denisekingsmill