A fast-food giant has committed to using only British potatoes for its fries – and one of its flagship suppliers sees it as an opportunity to build links between East Anglia's commercial farms and the diners eating their food.

The announcement made by McDonald's UK at the height of the harvest will make the company one of the largest buyers of the nation's potatoes, through its two suppliers McCain Foods and Lamb Weston.

It will now be investing around £79m each year in the sector, sourcing from about 190 growers which meet Red Tractor assurance standards.

The restaurant chain claimed the move is proof of its commitment to remaining one of the biggest customers of British agriculture.

But for the growers, it is a chance to demonstrate that 'local food' does not just mean cottage industries and farmers' markets – it is a major resource valued highly by some of the world's biggest retail and food service brands.

Ahead of the announcement, a senior McDonald's director visited the Elveden Estate on the Norfolk/Suffolk border, to watch harvesting operations at the farm which supplies it with 9,000 tonnes of potatoes a year via McCain.

Although the nearest fast food outlet is only a couple of miles away at Thetford, farm manager Andrew Francis said very few people eating there would know how close they were to the fields where their fries were harvested.

He said: 'There are all sorts of levels to this. The primary one is simply to get people to realise that it is a potato in that carton of fries. The fact that it will be British can only help the industry, particularly when it is something positive like this that is sheltering us from the pressure of imported produce. And it is East Anglian, which is good for the region.

'We have McDonald's at either end of the estate so we could be growing their fries within two miles of those restaurants. People may not comprehend that, but if we can talk about local produce and local food then we can start to join things up.

'It shows all the different aspects of what we do in this region, from small niche artisan production, to international major brands – and doing it all sustainably.'

Elveden is certified as a Flagship Farm, part of a project developed in conjunction with the Food Animal Initiative (FAI) aiming to highlight best practice among the 500,000 farms across Europe which provide McDonald's with the raw materials it needs for its 7,000 restaurants. The scheme assesses farms based on their economic, environmental and ethical approach to food production.

'McDonald's have been doing this for a lot of years, but there is maybe not that linkage across to telling the customer in the restaurant that this is what goes into producing their food,' said Mr Francis. 'I would see them as one of a handful of customers we deal with who are pro-active in setting standards, who listen to the problems in the supply chain, and talk about how we can address them. We do the technical work with McCain on product development and choosing varieties, and we see senior decision-makers from McDonalds two or three times a year.'

On his visit to Elveden, Connor McVeigh, ‎UK supply chain director for McDonald's, said: 'Our customers like us to source locally wherever possible, and so we're pleased to announce that from September, the only potatoes we'll use for our famous fries will be British.

'A succession of wet harvests has caused the British potato sector great uncertainty in recent years, and so I hope our long-term commitment to only source from this country will give farmers the confidence to innovate and invest for the future.

'We have worked hard over 40 years to build a UK supply chain built on long-term relationships, which is why our support for the potato sector goes beyond just financial investment. The extension of our Progressive Young Farmer programme meets a real industry need to encourage young people to consider crop production including the potato and fresh produce sectors, as an exciting and rewarding career choice.'

Elveden supplies two varieties of potato for McDonald's – Shepody, which can be harvested early in the summer to meet the demand for new season potatoes, and Russet Burbank which is more suited to long-term storage through the winter to ensure a consistent year-round supply.

Mr Francis estimates the farm is about 55pc through its potato harvest this year – about a week behind where he would expect to be at this stage.

'In the spring, it was dry during the day, and cold at night, which slowed the crops down and then in August we had 30-plus degrees for two or three days, which also didn't help,' he said. 'So things were just a bit late to get to size and to set the skins.'