To succeed in a turbulent marketplace, even a business steeped in tradition cannot afford to rely solely on its hard-won reputation – it must adapt, evolve and overcome. And nowhere is that more true than at agricultural animal feed supplier Duffields.

The Norfolk family firm, which began life as a flour mill and grew into an EDP Top 100 business, is celebrating its 125th anniversary by publishing the story of how it changed with market demand and survived disaster and conflict.

Founder William Lant Duffield battled through bankruptcy, two world wars, floods and the depression, while the current company chairman Alistair Duffield's challenges have included swine flu, bird flu, foot and mouth disease and double-dip recessions.

But Mr Duffield, the fourth generation of the family to run the business, said the company has always been able to respond to quickly and take advantage of opportunities as they presented themselves.

'We wouldn't have been here for so long if we didn't adapt to changes,' he said. 'No business would, but it's particularly true in agriculture.

'We used to have a lot of mills in a row in Topcroft, Flordon and Saxlingham at the beginning of the 1900s, and my great grandfather (William Lant Duffield) used to mill in one for as long as the wheels were going round, then jump on his bike to catch the water at the next one. I think that's fantastic.

'My great grandfather took the risk to get it all going, but my grandfather, William Charles, was the real businessman. He was the first to really rev up production, and that's key to what we are doing today.'

William Charles Duffield served in Egypt and Palestine during the First World War, but after running a mill for five years in South Africa, he returned to Norfolk and leased Buxton Mill in 1924. While the farming community was affected by the Great Depression of the 1930s, Duffields consolidated its operating base, increasing productivity at its mills and acquiring more strategic locations.

When war broke out again in 1939, the company received a telegram advising that all grain stock would be retained under government control.

Mr Duffield said: 'After we got that telegram, it was completely controlled by the government at a fixed price. We had to tell them what our production capacity was for all our plants, at Buxton, Tharston and Saxlingham.

'It is unbelievable really. Something like that comes across and your total business ethic has to change overnight. But we survived it. That is the most important part.'

After the war, the family invested in growth in the 1950s and 60s. The capacity at Buxton Mill was doubled in 1951 and Saxlingham Thorpe Mill doubled its animal feed capacity in 1965.

But in 1968 there was more hardship to endure, as thunderstorms flooded the Tas Valley, causing £10,000 of damage to Saxlingham Thorpe Mill.

'In the 1968 flood, my father (Tony Duffield) had to park up and swim to work,' said Mr Duffield. 'We were 6ft under water and it ruined 300 tonnes of bagged meal, and the transformer which ran the mill was out of action. If I drove down here today and found 6ft of water, I wouldn't know where to start.'

The water authorities took action to prevent future flooding by realigning the river course on both sides of the new road bridge. This provided an opportunity for Duffields to fill in the original water course through Saxlingham Thorpe Mill as the river was no longer required to power it.

The 1970s and 1980s was a period of modernisation, and the flour side of the business was closed in 1991. 'I think my father thought we had to specialise in either flour or feed,' said Mr Duffield. 'We couldn't do both. So we decided to concentrate on feed. A lot of our flour customers were on the other side of the country, and that was a big reason for the change.'

Mr Duffield, 44, took over the business at the age of 27 and immediately had to make some difficult decisions in 1998, with reorganisation and redundancies necessary to set the business on the right track for the future. 'If we had not done what we did, we would not have been here today,' he said.

'I am the fourth generation, and every generation has all had its challenges, however big or small. But we each had to get through them somehow.'

Today, the company has an annual turnover of £65m, running a fleet of 32 lorries and employing about 135 people – half of them at the Saxlingham Thorpe headquarters, south of Norwich. It produces about 250,000 tonnes of feed each year for pig, poultry, cattle sheep, game and specialist sectors. It has also expanded beyond its East Anglian base after acquiring Pen Mill Feeds at Yeovil, Somerset, in 2004 and Grain Harvesters in Wingham, Kent, in 2009.

As for the future, Mr Duffield said he hoped that the family tradition will be continued by one of his three children: Florence, 15, Frederick, 12 and eight-year-old Edith.

'I am very proud that we are 100pc family-owned and entirely debt-free, which puts us in a very strong position for our future destiny,' he said. 'We have got a big asset base and a strong brand ethic and staff. I have got the baton for my generation and, if at all possible, I want to see that baton passed on to the next generation.'