WINE made from certain grape varieties always tastes better in winter. Tannat is one of them. Native to Gascony, it now even makes superb wine in far-flung Uruguay, but its heartland remains the rolling hills at the foot of the Pyrenees in Madiran and Saint-Mont.

Early in the autumn, just before harvest, on a day when the peaks of the high Pyrenees could be seen peeping through the early morning cloud that shrouds the valleys, I visited Domaine Capmartin, one of the best estates in Madiran. Simon Capmartin showed me round.

It had not been an easy season for organic growers like the Capmartins. The copper and sulphur sprays that are the mainstay of their defences against fungal diseases wash off in the rain.

And in 2012, even in the far south west of France, it rained rather too often. Despite this, the vines were in good health. The big bunches of Tannat with their small, intensely coloured berries looked to be in good condition, though not all the berries had ripened to the same degree, which means that the Capmartins were facing a tricky time in order to select only the best possible fruit before they could be loaded into the fermentation vat.

The Capmartin family have made wine in Madiran for many generations, but Guy, Simon’s father, worked away for a while, and when he returned, his ideas about how to make the best of the local fruit and conditions had changed. He decided to break away from the family vineyard and start again from scratch.

He bought a house with land and planted new vineyards to supplement parcels of existing vines, some of them very old indeed. He now has 18 hectares of vines.

He decided to increase the density of planting, believing that with more competition for nutrients, the plants would root more deeply into the clay limestone and flinty clay soils of the area. He also had the wisdom to stop carrying out a ‘green harvest’.

This is done by many wine growers, who wait until the grapes begin to store sugar and change colour and then reduce the number of bunches on the vine. By this they hope to concentrate the sugars and flavours in the remaining bunches.

Tannat, as its name suggests, makes big, beefy, deeply coloured, tannic wine. Bold claims a few years ago by a British scientist, Roger Corder, that some of the complex phenolic substances with which Tannat abounds are particularly good in helping to prevent heart disease, led to a new upsurge of interest in Madiran.

All that tannin means that it has the capacity to age for a long time in the bottle. But Guy was one of the first in the area to realise that careful winemaking could keep the harsher tannins in check and produce a wine that needn’t be cellared for half a lifetime.

In fact their standard blend, which is made from 80% Tannat with 20% Cabernet Sauvignon, is remarkably approachable. The 2009 has a lovely aroma and flavour of rich, spicy, dark fruits and tannins that are politely held in check. With venison, duck or goose it would be irresistibly good. It’s available at Carruthers & Kent for an eminently reasonable £12.99.

Sadly the richer, more expensive cuvees are not exported to the UK – a great shame because the powerful, complex Cuvée du Couvent 2010 is perhaps the best young Madiran I’ve ever tasted.

British importers are keen to persuade Guy and Simon to lower their prices and increase the quantity of what they make, but they are equally insistent that this would not be the best way to maintain sales of what is essentially a high-quality, niche product.

“In the last 10 years we’ve managed to make a big difference in the quality of our wine,” Simon said, “but it has meant a lot of work.”

As well as the red Madiran wine for which the area is most famous, the Capmartins also produce a very remarkable white wine, in sweet and dry versions, made from two other, superb, closely-related, local grape varieties, Gros Manseng and Petit Manseng, both sold under the catchily-named local appellation of Pacherenc-du-Vic-Bilh. The dry white is very fresh and zingy in a grapefruity kind of way.

The sweet wine is memorable for all the right reasons. The skins of both Petit and Gros Manseng are very thick, which means that they are unusually resistant to rot and can be left on the vine until they become gorged with sugar.

Harvest is usually not until November, but can be as late as this time of the year. The shrivelled, intensely sweet berries almost miraculously hang on to crisp acidity, which gives their wine a unique freshness. They are emphatically not ‘pudding wines’, but are magical with almost any cheese and some other rich, savoury or spicy foods.

The 2011 Domaine Capmartin, Pacherenc-du-Vic-Bilh ‘Doux’ (£13.49 Carruthers & Kent) marries the flavours of very ripe grapefruit with fresh mango. It’s tangy, sweet and perfectly balanced.

I cannot pretend that it will be any kind of a benefit to health, but a small glass of this nectar has the power to brighten any winter day.