Andrew Nelstrop is unashamedly 'geeky' about the whole whisky-making process.

As the CEO of The English Whisky Company enthusiastically points out, it blends "chemistry, physics and logistics".

Back in 2005, their founder, Andrew’s father James Nelstrop, decided to fulfil his lifelong dream of making whisky.

Within a year he had built England’s first registered whisky distillery for more than a century, on family farmland near Thetford.

And at the beginning of this month, they launched their most exciting release to date: a 15-year-old single malt – England's oldest.

The extremely limited release of only 572 bottles worldwide has been matured in a bespoke sherry cask and is already sold out on their website.

According to the tasting notes, it gives off an aroma of dates, raisins and sultanas with waves of cherries, chocolate and figs on the palate.

Andrew describes the whisky as a “coming of age” for the company, which is in the process of being re-branded as The English Distillery.

When it comes to ingredients, all you need to make single malt whisky is barley, yeast and water.

And plenty of patience. There are seven steps in the whisky-making process - and the last of them can take between three and 50 years.

As Andrew explains, a portion of the barley used is grown on the family farms near Lincoln, with the remainder being sourced locally by the maltsters – either Crisp Maltings near Fakenham or Muntons in Suffolk.

Once the barley has left the farm and travelled to the maltster it under goes the process of malting. And here comes the science bit.

“The malting barley is soaked with water and laid out on the floor where it chits, just like cress on blotting paper, which most of us did at home as kids,” explains Andrew.

“Once chitting starts, the barley is turned to break the chits off and stop it growing into a big green carpet.

“After all the barley has chitted, it is dried out by blowing warm air over it. This is the malting process finished,” he continues.

“The act of malting has changed the starch in the seed, which will allow the distillery to covert the starch into sugar.”

Once the barley arrives at the distillery it goes through a number of processes. First of all, it is milled to break open the grain.

“We are not making flour – it’s more like cracking pepper in a pepper grinder you have at home,” explains Andrew.

Next the milled barley is mixed with hot water – a process known as mashing. The water comes from a stream under the distillery site at Roudham, near Thetford.

“As the hot water mixes with the grain, the starch in the malted barley is converted to sugar and the resulting sugary liquid is collected by us to continue in the process,” says Andrew.

“This sugary liquid is officially called wort. It is best visualised as Horlicks, as it is a malty, sweet liquid.”

The wort then goes to the fermenters.

“In the fermenter we add some yeast, similar to the bread making yeast you might buy at the supermarket,” says Andrew.

“Over the next 24 hours, the yeast reacts with the wort and all of the sugar is converted to alcohol; then for the next 72 hours more fermentation takes place locking in additional flavours. The end result, some 84-96 hours later, is a cloudy 7% alcohol liquid officially known as wash; in reality, this is like a cloudy real ale.”

The next stage is distilling.

“The wash is pumped to the first copper still and distilled, where the wash is concentrated up to about 22% alcohol,” explains Andrew. “Still not strong enough to become a whisky, but it is now quite clear and starting to taste like a weak whisky.

“This 22% alcohol is known as low wines, which are then sent to the second still to be distilled again. This time the still takes it up to 72% alcohol and the resulting liquid is perfectly clear, like gin or vodka, and now tastes like whisky.”

With the work of the distillery floor done, the spirit is sent to the casking room – which is where patience comes in.

“The 72% alcohol spirit is reduced to 63-68% alcohol and put into a wooden cask,” says Andrew. “The wooden cask is rolled to the maturation shed, where it remains for between three and 50 years!

“All of the colour in the whisky is imparted by the wood and its previous use. So, for example, a cask that previously held red wine will result in a pink whisky.”

While maturing, the casks breathe so some whisky evaporates each day – this is known as the angel’s share.

“In Scotland about 2% a year evaporates to become the angel’s share,” says Andrew. “But in Norfolk, due to our climate being warmer and drier, we lose around 5%, resulting in our whisky maturing faster. So, a five-year-old in Norfolk is about the same level of maturity as a 10-year-old in Scotland.”

Many years later – with whisky production you really are playing the long game – the cask will be tasted and if it’s deemed to be ready, it will then be bottled ready for sale.

“Once the whisky is in the bottle is no longer matures,” says Andrew. "So a 10-year whisky that has been in the bottle for 30 years is still a 10-year-old whisky, unlike wine.”

As well as making single malt whisky, at The English Distillery they also make what they call the Norfolk Grain Whisky trilogy.

Reflecting its Norfolk home in its branding, its logo is a seal – huge numbers of which live round the coast – wearing a bowler hat, one of the county’s most famous exports.

The Norfolk Farmers - Single Cask is a golden whisky, which has wafts of chocolate, apples and custard tart, while The Norfolk Farmers is spicy and oaky with notes of buttery popcorn. And the sweet, spicy and dry Norfolk Parched has a hint of brandy snap biscuits, and a slightly nutty character.

Production of the 'trilogy' follows a very similar process – the only difference is that these whiskies are made from grains other than malted barley, such as rye, wheat and maize.

They also produce a range of liqueurs and creams. Made with their single malt, Andrew describes the hugely popular Norfolk Nog as “like a very posh Bailey’s”, which is delicious on its own – or as a treat to liven up an after-dinner coffee.

Some of their single malts are matured in Pedro Ximenez sherry casks.

Deciding that the sherry was too nice to leave behind, they decided to take it too – and added some of their single malt to it and left the casks to continue maturing, the result of which is their Norfolk PX.

Andrew describes it as being “like liquid Christmas pudding”.

And, perfect for this time of year, is The Norfolk Bramble – blackberries and English single malt, which can be drunk neat or added to a glass of fizz.

“Instead of sloe gin, this is blackberry whisky,” says Andrew.

Putting Andrew totally on the spot, what are his favourite whiskies?

“That’s like asking someone who's their favourite child,” he laughs.

“I love the English Rum Cask, it reminds me of rum and raisin ice cream. But over time my tastes are changing and we are always trying new things. Anything that has been in a sherry cask, I love.”

To find out more about The English Distillery, including their popular tours, visit englishwhisky.co.uk