Brewed with Lactobacillus – the bacteria found in natural yoghurt – this classic German sour beer style, which was dubbed “the Champagne of the North” by Napoleon's troops, has all but disappeared from its native Berlin.

Berliner Weisse typically finishes semi-dry, with low ABV, a crisp lactic acidity and gentle, delicate flavours. More modern variations – as with many sour beers – are commonly flavoured with fruit or flowers, but whereas, in Germany, this would traditionally be achieved with the use of sweet, flavoured syrups, Brew By Numbers use only natural flavourings and allow the sugars to ferment out, ensuring the finished beer is still sour.