When A Dawn, a painting by CRW Nevinson of haggard French troops marching to the front in 1914, was last sold in 1964, it fetched £300. Now regarded as one of the English artist’s finest works, and as one of the great paintings of the first world war, it is to be auctioned by Sotheby’s with a guide price of up to £1m.

“I hesitate to say a career-best, because it makes the rest of my career seem rather boring, but I never expect to handle a better painting by Nevinson,” said Simon Hucker, an expert at Sotheby’s on 20th century British art. “It is a great painting, every inch of the canvas fully resolved, down to the way the men break down at the very back of the picture into mere geometric forms

“Futurism, the art of the machine age, perfectly engaged to the mechanism of war, with men literally being turned into cannon fodder. There were queues for his exhibition of these paintings in 1916. They really touched something in the public.”

Nevinson, who died in 1946, said of the painting: “It happened that I was the first artist to paint war pictures without pageantry, without glory and without the over-coloured heroic that made up the tradition of all war paintings up to this time.”

He saw such scenes from close up. He was in France as a volunteer ambulance driver within weeks of the outbreak of war in the autumn of 1914. “No man saw pageantry in the trenches,” he recalled.

Hucker said: “He was there so early that the British troops hadn’t really arrived in numbers. These unfortunate French troops are conscripts, with no choice about where they are marching.”

Nevinson’s reputation and prices have been rising steadily in recent years. Sotheby’s sold a small pastel, Troops Resting, at a record price for the artist of £473,000 in 2016. A Dawn will be in the Modern & Postwar British Art sale on 21 November, and Hucker expects keen interest, especially from nations whose troops were about to be sucked into the war alongside the wearily marching French soldiers.