Health poster promoting more fruit in the diet, 1920s, artist Joseph Moran

One of the public health lessons of the First World War was that the nation's young men were not as healthy and fit as the myth of the fighting British race suggested. But they were healthy & fit enough to serve as cannon fodder. In the interwar period, fruit was promoted as a way of improving health and fitness. It didn't hurt that it also sold cases of apples and pears produced by Kiwi growers.