Storied vintage at Portuguese winery

Necessity might be the mother of invention but pure chance can also play its role. Such was the case for Portuguese winemaker Jose Maria da Fonseca, who set up a winery in the Setubal area in 1834.

Some time later, seeking new markets, Fonseca started shipping his wines overseas, primarily to Brazil. Not all were sold, and the remainders made the long journey back home across the Atlantic Ocean, crossing the tropics and the equator along the way.

In theory, this long, arduous boat trip - with its drastic temperature variations, the motion of the sailing ship and exposure to sun and sea air - should have proved detrimental to the wine, usually aged and stored in such carefully controlled conditions. But in this case, the opposite was true: the moscatel fortified wine improved in taste, having aged the equivalent of decades in mere months.

"It was quite a surprise," admits Rita, our tour guide at Fonseca's eponymous winery, still in operation 180 years later in the village of Azeitao, about half-an-hour's drive south of Lisbon. We're here today for a tour of the winery as part of a seven-day trip through Portugal and Spain with luxury coach touring operator Insight Vacations.

This is one of the Signature Experiences offered to Insight's guests, designed to go beyond the big-name attractions and provide a deeper understanding of the destination.

As Rita tells us, the well- travelled wine was named Torna Viagem (Portuguese for "return journey") and, more than a century later, so intrigued the Jose Maria da Fonseca winemakers that they decided to repeat the process. In 2000, six 600-litre casks of 1984 moscatel sailed to Brazil on a tall ship owned by the navy, and the effect was the same. "It's really something we can never reproduce here at the winery," Rita says. Some of the original 19th century Torna Viagem remains in the winery's cellars for comparison.

The process has been repeated since, again in partnership with the navy, although Rita says there is always less wine in the barrels when they return than when they left. It's not that the naval officers get thirsty, she explains - it's the evaporation caused by the variable maritime conditions.

Torna Viagem is not available for sale but it's only one of more than 30 brands produced by Jose Maria da Fonseca. Chief among these are its Setubal Moscatel fortified wines and the Periquita label, created in 1850 and, the company claims, now Portugal's oldest brand of table wines.

Standing in the winery's museum room - filled with photographs and other memorabilia relating to the company's history - Rita tells us that Periquita was also Portugal's first-ever bottled red wine. Jose Maria da Fonseca learnt about the technology in France and brought it back to Portugal. Prior to this, Rita says, wine was sold in barrels, but the advent of bottles and corks meant the wine couldn't be modified later on by unscrupulous agents.

The Periquita range now also includes white and rosé varieties, and remains the brand which the winery produces and exports the most - some 80 per cent of production heads abroad. And while the brand remains a constant, other things at the winery have changed considerably in the intervening years. In the late 19th century, Rita says, the winery could produce 200 bottles a day. Now they can pump out approximately 30,000 each hour, making them one of the biggest wine producers in Portugal.

From the museum room, we head into a neighbouring cellar, where we see the barrels of Torna Viagem, before ducking outside to the Periquita and other cellars. They're atmospheric places, dim and a little musty on this rainy late-autumn morning, pungent with the grapey smell of maturing wine.

In one, we see massive 18,000- litre barrels made from Brazilian mahogany, which have been in constant use for about 60 years, and in another we tread carefully on the dirt floor between neat stacks of smaller barrels covered in dust and cobwebs.

Here, behind locked metal gates, Rita shows us where some of the oldest and most valuable wines are stored (she recalls one selling at auction not too long ago for about �, or roughly $2800). The mood is enhanced by wafting Gregorian chants which, Rita admits, create ambience rather than playing any particular role in maturing the wine. This building, dating from 1750, is "considered like the cathedral or temple of muscatel wine", she explains.

Jose Maria da Fonseca continues to be a family owned company, and we're joined here by Sofia Soares Franco, part of the seventh generation to work in the family business. She's full of enthusiasm for the company but says it was by no means certain she would get involved, having completed a political science degree and worked for NATO in Lisbon prior to taking on a role here as wine tourism and communication manager.

We finish in the shop, where we browse the range for sale - everything from the well-known, easy-to-drink Lancers series to a high-end muscatel retailing for � a bottle. We also have the chance to sample three of the company's wines: the Periquita 2013 Branco white, the Periquita 2012 Reserva red and the Alambre 2008 Moscatel de Setubal. I'm no expert, but they're all a nice drop - all the more so thanks to the stories behind them.

• fact file *

·For Jose Maria da Fonseca, see jmf.pt.

·Insight has a range of tours visiting Portugal in 2015. For example, the nine-day Amazing Spain and Portugal itinerary visits Lisbon along with Seville, Madrid, Granada and Salamanca, and costs from $1975 per person twin share (single supplement from $370) including eight nights accommodation. Or, the 10-day Country Roads of Portugal trip, which includes stays in Lisbon and Evora among other destinations, costs from $2625 per person twin share (single supplement $780). insightvacations.com or 1300 301 672.

Gemma Nisbet travelled as a guest of Insight Vacations.