Mr Letts developed the grain in frustration at the modern types of wheat grown in the UK, which produce straw too short for use as roofing thatch. He believed using older varieties where you could get two products from the land was better for the environment.
He scoured gene banks and traditional farms across the world to track down tall varieties of wheat, like those grown in medieval times.
He said: “After so many years of struggling to research this and develop it, I think it’s catching on.”
The grain is being grown on farms at Faringdon and Wheatley, producing 1.3 tonnes of grain per acre plus the same weight in thatching straw.
He said: “I think the bread’s delicious and most people really like it.