Her company has been used by politicians and business tycoons the world over to improve the way they present themselves. “But I’m not allowed to tell you which ones - silence is part of the contract.”

At the Independent Schools Association’s annual conference in Buxton last Friday 100-plus delegates crowded into the lecture room at 9.15am sharp, dressed to kill. Well, they gave it their best shot.

Ms Spillane complimented them and promised that the following hour would change their lives, acknowledging that taking presentation skills seriously did not come easily to the British. But the Harvard-educated American who has lived here for 15 years added: “I have never known a nation so keen on sizing people up by the way they dress or speak.”

She reminded them that Parliament had talked of introducing a dress code for teachers. (David Shaw, Conservative MP for Dover, failed to get an amendment passed in the Education Bill last year, but the attempt gave rise to “scruffy teacher” headlines.) And she found that employers rated communication skills and image higher than training in future employees. “Human resources managers tell me they decide against a candidate in the first few minutes: we live in a tremendously visual world.”

What five buzzwords would the heads choose to sum up the values they wanted to project to parents? she asked. “Warmth”, “efficiency”, “professionalism”, “success”, “security”, were some suggestions.

Tony and Davina were summoned to the front of the class to demonstrate these attributes. Tony’s dark grey suit (“Button your jacket . . . Good, it does”) could be enlivened by a brightertie. As it’s spring, maybe he could try a lighter grey or “one of those new sludgy colours”, she suggested, draping bits of cloth over his shoulder.

Davina’s violet suit with a white blouse met with approval: “You’re not dressed like a policewoman.”

Then the delegates had to carry out an “individual image audit”: a checklist on voice quality, written, verbal and social skills, table manners, eye contact, handshake, posture, fitness, grooming, style and manners. These were marked on a scale of nought for “a liability”, one for “on a par with peers”, two for “above average” and three for “first rate”.

“Don’t be too British about this,” ordered Ms Spillane, adding that they should give this checklist to sixth-formers as they’d be surprised how much these attributes counted.

So do colour and style: John Major no longer wears blue shirts as they make him look unshaven; everyone should wear a jacket, always buttoned up when addressing an audience otherwise they pull attention away from the face.

Women should avoid looking “mumsy” - “Do you want to work for your mother?” - and clothes should be appropriate for the sector they work in. “Leather mini-skirts won’t cut it with the board of governors”; “Flowers are not professional”.

Those who use make-up get promoted sooner, but should take care not to leave their cosmetics stuck in a time warp: “When did you last see blue eyeshadow?” Unless you are Richard Branson, shave off the beard. Despite the substantial sprinkling of (well-groomed) beards in the audience, the heads lapped up the advice.

“It certainly makes you look at people differently,” they murmured on their way to coffee.