Staff who work at Kettle Foods are passionate about the quality of their crisps, which come in nine flavours – lightly salted, sea salt, and balsamic vinegar, sea, salt with crushed black peppercorns, mature, cheddar and red onion, sweet chilli, sour cream and chive, honey barbecue, red Thai curry and no added salt – as well as in limited edition seasonal flavours which are brought out twice a year.

The factory uses 50,000 tons of potatoes to produce 60m bags of crisps a year and Kettle Chips is now one of the most popular snack brands in the UK.

Although Kettle Foods has embraced automated processing systems to meet demand, the old fashioned hand-cooking quality has not been lost, and it does not use artificial flavours or new hybrids of chipping potatoes which have been developed for other brands to provide a pale, uniform colour.

The technology used by the company, which produces a wide variety of crisps, vegetables and nuts, has come on in light years since the factory opened in 1988, but the staff are adamant the crisps are still of the same quality.

The process of making the traditional crisps begins when thousands of potatoes, which are a variety chosen for their size and flavour, arrive at the factory where they are unloaded from huge storage containers, cleaned and checked for defects.

They are sent whizzing through a water transportation system to avoid bruising and arrive at the drumshaped pieces of equipment lined with vicious looking razors dropped through them, slicing them to a carefully determined thickness.

The distance between the razors is carefully measured and they need to be replaced every few hours because they are blunted so quickly.

As the potatoes fly out of the slicers, they fall into vats of sunflower oil, where they are cooked until they are golden brown and raked to ensure they do not stick together.

Once out of the fryer, the potato slices are taken across the factory by conveyor belt where they are analysed by workers for colour and quality. Any which are stuck together are removed by hand, as they are unlikely to have been cooked properly, and crisps are rejected if they are too small, too thick or the wrong colour.

Those crisps that make the cut continue their progress across the factory and pass through drums where salt and seasonings are added, before the completed snack drops into a bag, which is sealed, stamped, and boxed.