The surprising secrets behind Britain's favourite biscuit, as McVities chocolate digestive turns 100

Daily Mail​

26-04-2025

Every morning, for the past ten years of mornings, I have eaten a dark chocolate digestive biscuit. I don't really know how or why this habit started, but it did. I eat my daily digestive before I eat anything else and it is – I am convinced of this – good for me; it's structural, grounding. Also, it's not, actually, excessive. Each morning I limit myself to just one solitary biscuit, cold from the fridge, broken in half and eaten in bed.
But one morning earlier this month, I was faced with millions and millions of them – and all before midday.
To explain: this week the McVitie's chocolate digestive turns 100. To celebrate I visited the company's factory in Harlesden, Northwest London – the second largest biscuit factory in the world. The largest is the Chicago factory of Nabisco, whose biscuits include Oreos. McVitie's factory measures 50,000 sq m, the size of seven football pitches; Nabisco's is 170,000 sq m.
At Harlesden, wearing a hi-vis vest and hairnet, I walk around the site with Nina Sparks and Fraser Jones, two McVitie's managers who have worked at the company for 27 and 28 years respectively. I ask how many chocolate digestives they think they eat in a week and Jones says, in a wistful voice, 'Well, I weighed about 11 stone when I started here.' Sparks remembers being pregnant and developing an intense craving for Rich Tea biscuits. 'I would go down the lines and just look at them. Rich Teas got me through my pregnancy.'
The factory is open 24 hours a day, 362 days a year – Christmas Day, Boxing Day and New Year's Day excluded – and most of the around 600 staff work 12-hour shifts, two days on, two days off. It produces 13 million chocolate digestives a day, as well as 12 million plain digestives, ten million Rich Teas, four million Chocolate Hobnobs, and 50 million Mini Cheddars. The latter tumble out of a gigantic oven like coins from a slot machine.
Making a chocolate digestive works like this. First, the ingredients arrive by truck at the factory. While the chocolate obviously comes from abroad (often Ivory Coast), the base ingredients are harvested in Britain. The batter consists of, roughly, plain flour, wheat flour, vegetable oil, sugar, raising agents and salt, and it is prepared in two enormous mechanical food mixers. (The presence of fats and additives means a dark chocolate digestive scores a 'bad' 18/100 on the food rating app Yuka. But this neither bothers nor surprises me, given it is a delicious chocolate-covered biscuit.)
Once mixed, the batter plummets down a tunnel, is flattened by a machine into a dough, then cut by another machine into 67mm-wide discs. Any excess dough is collected and transported up an electric helter-skelter where it is reused. After it's been stamped with holes to stop it from over-rising, the biscuit travels by conveyor belt into an 85 metre-long oven, moving forward constantly as it cooks. Here, Jones suggests I try a biscuit, fresh from the oven and straight off the factory line. Quickly, I pick one up. It's so hot it hurts to hold. It tastes fantastic. A man in a lab coat approaches the conveyor belt and plucks a biscuit off it, too. He is a quality checker and he does this every 15 minutes – taking a cooked biscuit to a special station, where he analyses its colour under what looks like a microscope, then crushes it up in a bowl, prodding a rod-shaped gadget into the granules and assessing its moisture levels.
On the conveyor belt, the biscuits keep advancing – through a cooling machine and then over what look like rows of miniature train tracks, bubbling with liquid chocolate. This step of the process covers the biscuits' undersides in a bumpy layer of chocolate, which, Jones explains, is partly aesthetic (the ridges catch the light) and partly practical (it increases the chocolate's surface area). McVitie's refines and tempers its chocolate at the company's Manchester factory, transferring up to 60 tons of it a day to London. The lorries go in the middle of the night to avoid the traffic.
The next stage of biscuit-making is complicated. Until now, the chocolate digestives have travelled on the conveyor belt as a mass, but in order to get into packets they need to be separated into several uniform lines. So they move off the conveyor belt and on to a sloped metal track, which is divided into lanes. As they slide downhill, the biscuits gain speed and bump against each other, falling naturally into place. There are tricks to reduce friction – cold air, for instance, is blasted underneath the metal track – but there's trouble if even one biscuit gets stuck. It can cause a pile-up that can lead to thousands of damaged and unusable biscuits. I ask Jones if he can recall the biggest biscuit car crash of his career. How many chocolate digestives might have been crushed at this stage in the process?
He umms and ahhs. A lot? He gives an almost imperceptible nod. 'I'll leave it at that.'
From here, everything is mostly done by robots. They wrap the biscuits in plastic (16 per pack), then put the packets in boxes, the boxes on pallets, and the pallets in trucks. The whole process – ingredients arriving, biscuits being made, products being shipped – is dependent on all of its parts functioning. 'We had this discussion during Covid: if the world comes to an end and everything stops, how long can we keep running for with the stock we have?' says Sparks. 'We landed on 18 hours.'
McVitie's began in Edinburgh in 1839 with a baker called Robert McVitie. But it wasn't until 1892 that the company began selling digestives. It's unclear who exactly invented the biscuit (records suggest digestives were first made by a duo of Scottish doctors in 1839, who claimed the bicarbonate of soda present in the recipe aided digestion). Either way, McVitie's made it popular. And in 1925, employee Alexander Grant had the sense to coat a plain digestive with chocolate.
Today, McVitie's sells £157 million worth of chocolate digestives a year; according to the firm's data, one in three British households consumes a £2.25 packet a week. Of those, around 80 per cent are milk chocolate and 20 per cent are dark. Out of interest, I looked at Sainsbury's customer reviews for McVitie's milk chocolate digestives. And, while it may be strange to leave a review for the most famous biscuit on earth, they're all positive; 313 in total and a 4.7-star average. 'Very good and crunchy,' says one. 'What a brilliant biscuit!' says another.
When I leave the factory, I say to Sparks and Jones that I don't think I'll ever eat my dark chocolate digestive in the same way. And the next morning, as I have my ritual biscuit, I think about the process that brought it here: the flour being harvested in the fields, the tons of chocolate travelling down the motorway at night, the conveyor-belt oven, the packaging robots. The fact that, as I break the biscuit in half, all of this is happening right now, and will continue to happen every second of the day until Christmas Day, is a bit dizzying and also amazing. As that wise reviewer put it, what a brilliant biscuit!
McVITIE'S IN NUMBERS
£2 billion
The price paid by Turkish company Yildiz in 2014 to acquire United Biscuits, which includes McVitie's.
1902
The year McVitie's opened its Harlesden factory in London.
6.5 minutes
Amount of time a digestive takes to cook (at 280C).
47 years
The time its longest-serving employee has worked at the factory.
0.6%
The waste McVitie's creates a year. It resells faulty biscuits to animal-food companies.