Brewers use specially selected varieties of barley that are particularly suited to being malted – a process that starts to release the sugars essential needed for fermentation.

But any cereal or mixture of cereals could be used to make beer, and it is not uncommon to find beer recipes that may include maize, rice, millet, oats, rye and wheat.

Hops are used like a spice. Normally they are harvested in the late summer and dried and traditionally they were packed into large tall sacks called pockets.

Today hops tend to be compacted into pellets and vacuum packed in foil, like coffee, to preserve their freshness.

The water used in a beer, is of course only a small proportion of the water used by brewers.

An efficient brewery will use between 5-7 litres of water to produce one litre of beer, the remainder being needed for heating and cooling, and for washing brewing equipment and containers to ensure absolute cleanliness.

Yeast is a microscopic member of the fungus family, a living organism it converts the sugars obtained from the malt into alcohol - a process called fermentation.

The Latin name for brewing yeast is Saccharmyces cervisiae – literally beer sugar yeast.

Yeast also produces a vast range of flavour compounds and much of the subtlety of beer comes from the yeast strain and the fermentation conditions.

Brewers use their own strains of yeast, which they look after with tender loving care as they produce the distinctive flavours of their own particular beer brands.