In 1942 Lord Halifax, Britain’s ambassador to the United States, told a leading group of American scientists that it was difficult to exaggerate the importance of the chemist, the engineer and the inventor – ‘the backroom boys’ – to the British war effort. David Edgerton’s Britain’s War Machine is a paean of praise for ‘these backroom boys’ and many little known heroes emerge from his pages.

In his previous work Edgerton has already helped to redefine the history of technology. And there is much to admire in Britain’s War Machine – for instance the thorough scholarship and the references to such a variety of sources. On one page Edgerton is quoting a Movietone newsreel, on the next he is trawling through the papers of an industrial scientist. And the book sings with a litany of British technology, like the Merlin engine, the Napier Sabre or the names of once famous companies like Pye, EKCO and ICI. There is also a great deal about trade and about Britain being at the heart of a great global empire. But what I really like about Edgerton’s approach is that he sees wartime technology not just as a story of the new and the modern but of the totality of machines that were used in Britain during the war. His is a story of tramp steamers and Liberty ships, as much as it is of new aircraft, missiles and scientific breakthroughs.

But it is as though he has been given the instruction to ‘go forth and debunk’. On almost every page Edgerton is busy telling us that what we used to think is wrong and that he has the correct way of understanding the Second World War. He begins by making it clear that Britain as the plucky underdog in 1940 is a myth. That’s not exactly new but Edgerton tells us how powerful the British economy was at the start of the war and how confident many people felt of British technological superiority over Germany, what he calls the ‘assurance of victory’. Although this didn’t last long when the guns actually started firing Edgerton goes on telling us how the British Army was far more tank-centric than the German, how Britain was at the centre of a vast arms industry (what he calls the ‘warfare state’) and how Britain produced more aeroplanes and warships than Germany for most of the war.

The real defeats, he argues, came not in 1940 with the fall of France but in the disasters of 1942 that fundamentally weakened the empire. Right to the end of the book he is exploding myths, such as the one that Britain had mobilised its women for war more extensively than other warring nations. All of this is backed up with a mass of statistics that is not always convincing. When, for instance, he argues that views of wartime nutrition are all wrong he makes many interesting points. But when he says that imported food was available in large enough quantities to keep the British population ‘very well fed’ you wonder if he has ever spoken to anyone who lived through the war. Like a lot of this book the general point Edgerton makes is often fascinating but at times he swings the pendulum too far to make his argument convincing.

He keeps telling us about Churchill’s inventiveness and his enthusiasm for scientific ideas to give Britain an edge. But then he explores the bizarre and crazy ideas that only diverted resources. Of course this is all part of the process of invention, as so many new ideas fail and no one knows at the beginning whether an idea will win the war or end up on the scrapheap. But to spend so much time on Nellie, the giant trench-digging tractor, or on rockets that never really worked and on Habbakuk, the giant iceberg aircraft carrier, is unfair to Churchill. The prime minister had the rare ability to push the mavericks around him to come up with some of the greatest wartime weapons and ideas. And I cannot accept, as Edgerton argues, that Mulberry, the giant concrete and steel harbour that was sailed in pieces across the Channel after D-Day and assembled off the captured beachhead, was a waste of effort. This was a major project that was so vast in scale it would have doubtless been abandoned at an early stage without Churchill’s ardent support. It was used to offload men and materiel at Arromanches for the next six months until harbours were captured in north-east France and Belgium.

However, although he sometimes overstates his case, Britain’s War Machine is a major new assessment of Britain’s war effort from 1939 to 1945. Never again will some of the lazy assessments of how Britain performed over these years, often based on postwar propaganda, be acceptable. That’s why this is such an important new book.

Taylor Downing's new book is Spies in the Sky: The Secret Battle for Aerial Intelligence in World War II (Little, Brown, 2011).