I've written about urban winery London Cru several times before. They are by no means the only city-based winery in the world, but they do have a unique twist: the grapes they ferment are imported from different countries.

By hand-picking the fruit into small plastic crates and using temperature-controlled trucks, they are able to get fruit from vineyards in Spain, Italy and France to southwest London within 24 hours and without compromising quality. In fact, such a journey is not unusual within mainland Australia, for example. But there is no need to defend or discuss this practice much, because the quality of the wines speaks for themselves.

I've tasted everything they've produced there, starting from the 2013 vintage. The highlights have included the 2013 Cabernet Sauvignon from the Roussillon, the 2014 Barbera from Piemonte, as well as the 2014 Syrah and Grenache from Calatayud. In every case, the wines delicious and reflected their respective origins and varieties very faithfully.

The only problem from the market's point of view is price. Retailing between £15 and £20 per bottle, these wines operate in a hugely competitive sector. They are not bad value for money, especially with the added value of their intriguing background, but there are plenty of similar wines of similar quality at similar prices available on our shelves. It's never easy selling wine at this price, whatever your story.

With the 2015 vintage, however, there has been a breakthrough. The principle stays the same: grapes have been sourced in mainland Europe, imported to Britain and vinified at the winery in London. The difference is found within the bottles of Charlotte St, their 2015 Chardonnay from Limoux.

The quality of this wine is not just the best they've produced but - and this is the really important point - significantly better than most of the Chardonnay made in situ. In fact, it's a whole lot better than Chardonnay made from a whole host of places, and it even has the intrinsic quality and complexity to challenge famous names from Burgundy.

How have they done it? Not through any nefarious trick, but via the same simple principle that governs every great wine: using top-quality fruit. It helps that the 2015 vintage was a good one across Europe, but there has undoubtedly been some astute sourcing from the London Cru team, led by winemaker Gavin Monery.

The winemaking follows standard quality Chardonnay procedure: whole-bunch pressed, 100% barrel fermentation with partial wild ferment, eight months maturation on gross lees without bâttonage, and partial malolactic fermentation. None of that really matters, though. What matters is the finished product.

It really is a stunningly good Chardonnay, with an incredible amount of fragrance and fruit ripeness - especially considering the stated alcohol level is only 12%. The oak integrates seamlessly, giving a lightly toasted aroma as well as smooth grainy texture. The impressive persistence and savoury, flinty finish is a real hallmark of quality in Chardonnay - this is a wine of place, not production.

Creating a French Chardonnay in London that outshines so many made in the country where the grapes were grown is a proper breakthrough. It's a triumph for London Cru, and a must-try for any lover of sophisticated Chardonnay.

The wine will go on sale in late 2016 or early 2017 - but in the meantime, their excellent 2015 Albariño from Rias Baixas is available to buy now, and also comes highly recommended.