It’s not just that a good suit makes a man look professional – it also gives a psychological benefit. It offers protection and even generates respect, and you need more of that when tough times bring insecurity,” says Frederik Willems, head of design for Savile Row tailors Gieves & Hawkes. Small wonder then that, after years of softening dress codes and the casualisation of the workplace, the recession has brought renewed interest in dressing up for business – a need for workers to retrench in conservative attire and to stand apart from those whose sense of propriety went out as Dress Down Fridays came in.

The need to dress up for the downturn comes at a bad time for the wallet. The New Year may bring a determination to overhaul the wardrobe, but that means spending when saving may be more sensible. “The answer,” says Archad Mahmood, managing director of London tailors Apsley, “is the investment suit. Rather than buying three or four from the high street to last the year, buy fewer and better.”

Recent years have seen a decline in the spend on suits: the UK market, valued at £162.2m in 2007, was down 10.2% in 2009 to £152m (€168m), according to market researchers Mintel, a drop attributed less to men needing fewer suits as deciding to defer replenishing. Shop clever in the first place – with, as Willems notes, a regard for “craftmanship over throwaway fashion that sees a suit fall apart in two months” – and yearly replenishment may even become a once every decade event.

According to Mahmood, the primary consideration in any investment suit should be the fabric, which accounts for the bulk of difference in price between suits. He advises opting for at least a 12oz fabric, “because the heavier the cloth is, the longer the suit will last, and the more capable it will be of being worn day-in, day-out”. A 9oz cloth of the kind typically used for high-street label suits will not only crease more easily and sag faster, but feel too lightweight in winter; in contrast, a 16oz fabric will be close to bulletproof but loses year-round utility – unless you happen to be a moorland gamekeeper. Opt for an English worsted pure wool cloth; vicuna, cashmere or cashmere blends may give sheen and softness but at a heavy price to durability, while polyester mixes trap perspiration and quickly degrade the fabric. “Even silk mixes are a bad idea,” says Ajay Mirpuri of tailors Raj Mirpuri. “No matter how sleek the suit looks on the hanger in the shop, after a few wears and some ironing it will go shiny. Mixes are for special occasion suits, not the everyday.”

The way your suit of choice is made is equally important. Mirpuri recommends, if at all possible, upgrading to any suit that does not use a fused construction (a good sign is whether the front and rear fascia of the lapel can be gently pulled apart), since in time this will see patches bubble up, especially if the suit gets wet. “There’s no point having a great fabric if the suit is fused,” says Mirpuri.

Style, of course, is the trickiest factor, given the unpredictability of fashion. Most tailors suggest opting for a dark colour – navy or charcoal grey but never black (“it’s very Tom Ford but best seen only at funerals,” says Mirpuri) – because this will best carry from breakfast meetings through, if necessary, to evening functions.

A herringbone pattern looks plain from a distance but adds texture and interest. And, contrary to any inclination to get more fancy detail for your money, this should be avoided: no dramatically slanted pockets, contrast coloured button-holes, linings or trims.

Mirpuri adds: “It’s ironic but the idea is to make an investment suit as unmemorable as possible; that makes it best for framing different shirts and ties. Colleagues should not be able to see you’re wearing the same suit. And, believe me, no matter how restrained from the outside, if your suit has a yellow lining, they will remember it.”

Naturally, style is important. Flat-front trousers without turn-ups, and a two-button, single-breasted suit with two side-vents is considered modern classic and provides the best overall tailored silhouette. John Hitchcock, managing director of Savile Row stalwart Anderson & Sheppard, says double-breasted suits are hardest to fit and so best avoided. Good fit is more important still: an ill-fitting suit not only looks discreditable, but will wear out faster. For those on a curtailed clothing allowance, buy a suit with a jacket that fits well across the shoulders and have the waist taken in for a silhouette by a tailor – a €25 job.

Of course, the path to the ultimate investment suit is to have the entire garment tailor-made, and with bespoke options priced at as little as twice that of some fashion suits, that is sound financing. “With care, a classically styled bespoke suit can literally last a lifetime. We have clients who claim bragging rights about how old their suits are,” says Hitchcock. “Besides, you only have to put on a little weight and the ready-to-wear investment suit is no longer wearable.”

A fully canvassed suit – one with an inter-lining comprising some 3,000 or more hand-stitches – might be regarded as one with a top-spec engine, giving the suit sustained form and fit, and around which the shell can, if necessary, be periodically updated. Most bespoke suits have a leeway of 15cm built into the coat and 1ocm in the trousers, allowing the suit to grow with your waistline. Shoulders too can be widened or narrowed marginally as fashion might dictate. A handmade suit also allows for the reinforcing of the crotch – typically the first point to go on any suit, which is why the wise will buy two pairs of trousers for every jacket.

“We had a field marshal contact us recently to ask us to replace the lining in his blazer, which was starting to wear a bit thin,” says Mahmood. “We checked our records and he had bought it from us 35 years ago and had worn it every week since. Now, recession or not, that was a good investment.”