The useful thing to understand about St Barts is that it is France. The bread is French, the pharmacies are French, the wine list is long, and lunch is taken seriously and at length. For a man deciding what to wear in St Barts, this matters more than the palm trees do. The island's day is built around a table in the shade at about one o'clock, and the clothes that suit it are those of a Frenchman on holiday: a good shirt, worn open at the neck, with nothing about it that suggests effort.

The morning belongs to the beaches, and they differ enough to be worth choosing between. Gouverneur lies at the foot of a steep road and has no facilities at all, only sand, sea grape trees and clear water. Saline is reached on foot over a dune from a small car park and has no shade, so the walk back at noon is hot. Colombier, at the north-western tip, is reached only by boat or by a footpath of twenty minutes or more. Shell Beach is a short stroll from the harbour. PP natural swim shorts in Oyster or Roosewood Pink are the garment for all four; they are 100% Belgian linen and are found in the natural swim shorts collection.

Then lunch. St-Jean, the long bay beside the island's famously short runway, is where the beach restaurants are, and where a meal can last until the music is turned up in the late afternoon. Swim shorts stay at the water. At the table a man wears a shirt and dry shorts: a Cuba Linen Shirt in Pink or Blue, or a Laos Short Sleeve Linen Shirt in Lemon Yellow, with PP linen shorts in White or Navy Blue. The PP Natural Set in White, shirt and shorts cut from the same linen, answers the same occasion with less thought. Colour is welcome here in a way it is not on quieter islands, and a pink shirt at St-Jean is simply correct.

Gustavia is the capital and the harbour, a small grid of streets around a rectangular basin. Its name, and some of its street signs, date from nearly a century of Swedish rule that ended in 1878. The red roofs are French West Indian; the yachts along the quay, particularly in the last week of December, are of every flag. Evenings begin here. The island's convention is firm on one point and relaxed on the rest: a jacket is rarely seen, and beachwear does not come to dinner. Linen trousers and a shirt with the sleeves rolled is the whole of the dress code, at the simplest bar and the most celebrated table alike.

For those evenings, the Monte-Carlo Male in Vanille, which closes with walnut buttons, or the Vibes Linen Shirt in Orchid, an oversized shirt that sits shorter in the body, with PP Trousers 100% Linen in White. The Bliss Linen Shirt in Dark Blue, long in the sleeve, is the one for a night when the trade wind is up. Underfoot, the streets are partly cobbled and the island is steep everywhere, so a loafer or an espadrille with a firm sole is wiser than anything delicate. The shirts are in the men's linen collection, most of them in certified Belgian linen.

The climate is steady. The dry season runs from December to April, with daytime temperatures in the high twenties, a constant breeze from the east and the occasional shower that passes in minutes. Summer and autumn are hotter, more humid and quieter, and some hotels and restaurants close for part of that period. The sun is strong in every month. The island is driven in small open cars, which leaves forearms exposed for longer than expected on the way to a far beach, and that is a practical reason to keep one long-sleeved linen shirt for the car as well as for the evening.

Two weeks in spring change the island's dress slightly. The St Barths Bucket, in March, and Les Voiles de St Barth, in April, fill the harbour with racing yachts and the quay with crews. Ashore the look becomes a degree more nautical, with pale shorts and plain shirts in white and blue, and tables are harder to find; dates are published well ahead and are worth checking. The quay at any time of year is described in what to wear in Gustavia harbour, and the island as a whole, for men and women, in what to wear in St Barts.

It adds up to a short list: two pairs of swim shorts, two of linen shorts, one of long trousers, five shirts in colours a man would not wear at home. St Barts is small, expensive and unexpectedly unpretentious about dress. It asks a man to look as if he had nowhere else to be, and to be on time for lunch.

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