The danger of candour, of course, is the exposure of flaws; and the opening pages of this book are already sufficient to put a sceptical reader, such as me, on high alert. (Here are my upward-facing cards: I am a moralist by profession, and I am very sympathetic to Newton’s intended targets.) To start with, those who rail against ‘convinced moralists’ are invariably quite as morally convinced as the objects of their sarcasm, only in the opposite direction; and Newton himself suffers no obvious lack of moral indignation.

Further, it is always a sign of weakness when a critic feels the need to caricature the opposition, manhandling them into straw men, since the need to fabricate a target suggests that the real one is impossible to hit. I have read all three of the ‘hawks’ whom Newton names – Gary Sheffield, William Philpott, and Gordon Corrigan – and with the possible exception of the last, who is not a professional historian, none of them is as crudely jingoistic as Newton would like his readers to believe.

What is more, the historiographical consensus that Britain’s belligerency was either realpolitisch necessary or morally just is much broader than Newton implies. In a BBC television debate last year, Niall Ferguson, feistily contending for British neutrality in 1914, found himself in an embarrassing minority of one. Even Christopher Clark (if he stands by his email to me) thinks that Britain’s participation was necessary.

Oddly, there is evidence of a counter-current beneath Newton’s mainstream argument, when he sometimes implies that he himself thinks that, when all is said and done, a good case for Britain’s belligerency can be made. ‘[E]ven nations very largely in the right can make terrible mistakes [my emphasis],’ he writes; and

Certainly, a case can be made that Britain ‘did the right thing’ on Tuesday 4 August. However, even accepting this, it is still essential to interrogate Britain’s role up to this point, and to ask what might have been done differently. Logically, Britain’s action on the last day of the diplomatic crisis cannot be assumed to vindicate all her actions over the preceding fourteen days. [my emphasis]

Indeed not, but this makes Newton’s thesis altogether less eye-catching and original. For he appears to concede that Britain’s eventual involvement in the war was probably necessary or justified, while contending that she made some significant diplomatic errors along the way. In that case, however, it is not actually the ‘hawks’ who are in his sights at all, but rather those who argue that Britain’s conduct of international relations in the fortnight preceding her declaring war was impeccable. (But does anyone actually argue that?)

This impression is confirmed when Newton tells us that ‘a key philosophic premise underpinning this work’ is that the search for ‘the incontrovertibly guilty men of 1914 is fruitless ... A focus upon wicked persons will produce such men in every capital city in 1914.’ Here Newton echoes fellow Australian Clark’s anti-moralising thesis exactly. For sure, this is a salutary corrective of the view that Berlin alone was guilty. Nevertheless, it is not obvious to me that any professional historian doubts that a measure of blame belongs in a variety of locations – not only Berlin, but also Belgrade, Vienna, and St Petersburg, perhaps even Paris and London. That said, the fact that blame’s spread is wide does not make it even: some might have been guiltier than others. It is quite possible that London both made some serious diplomatic mistakes and yet was right to go to war against Germany on 4 August.

While it is wise to refuse a simplistic moral judgement, it is dangerous to throw up one’s hands in despair at the difficulty of making a complex one – as Newton, following Clark, seems to do. The danger was made manifest in January 2014, when Die Welt published an article by three German historians and a journalist, who invoked Clark’s historiography in favour of renouncing the ‘moralisation’ of war altogether and returning to national realpolitik. The fact that realpolitik gave us the Western Front seems to have escaped them.

So candour entails costs. In the case of The Darkest Days, one of these is the exposure of the ambiguity of the book’s thesis and the shifting identity of its target. Still, some costs are indirectly fruitful, and here the exposure of the ultimate tendentiousness of Newton’s painstaking argument does the good service of revealing the truth of the very position he strives so passionately to dismantle.

What exactly is Newton’s argument? Through an hour-by-hour analysis of the British cabinet’s deliberations in late July and early August 1914, informed by heroic archival labours, he claims that Sir Edward Grey and Herbert Asquith, respectively Britain’s foreign secretary and prime minister, were committed to the Entente with France and Russia for imperialist, geopolitical reasons, and that they manipulated both the cabinet and parliament to make sure that Britain entered the lists on their behalf. It was this, and not the violation of Belgian neutrality that was decisive. At one point Newton effectively speaks through John Dillon, the leading parliamentary Irish nationalist. In a letter of 12 August 1914, Dillon wrote:

The violation of Belgium gives only a very convenient excuse ... to solidify the Party and the Country. I never had any doubt that Grey’s policy would end in a great European war. And that whenever it suited Russia to advance – then we would sink and would inevitably go in ... The blame is hard to apportion – no doubt – the German war party must bear a good share. But I cannot resist the conviction the greater share of the guilt lies with the new English foreign policy identified with … Grey.

But Dillon was wrong, although The Darkest Days does not allow the reader to see why. This is because its author does not pause to analyse the nature of Grey’s commitment to the Entente, thus leaving the reader with the impression that it was unconditional. That impression is false. Grey’s commitment was to France rather than Russia, and it was not unconditional. He assumed, correctly, that France was not planning to launch a first strike on Germany. Notwithstanding Poincaré’s bellicosity, Paris deliberately kept one step behind Berlin in her military preparations, so as to make her defensive posture unmistakable. As late as 1 August, she reaffirmed the order for her troops to stay ten kilometres back from the Franco-Belgian border.

At the same time, Grey strove to discourage Germany from precipitating war with France by refusing to promise British neutrality. Nevertheless, on 3 August Germany launched an unprovoked attack on Belgium and France, claiming that French troops had crossed the border and French aircraft had bombed Nuremberg. Both claims were fabricated.

In case this reading seems like the familiar fruit of British prejudice, let me invoke a leading German World War I historian. A critic of Clark’s thesis, Gerd Krumreich wrote in Le Monde last March that, while both sides had piled up the gunpowder in the years preceding 1914, it ‘is incontestable that it was the Germans who set it alight’.

Why did Germany invade? Because she feared that France would attack in support of Russia. According to ‘just war’ morality, however, the mere threat of attack is no just cause for war. Only if there is substantial evidence that an unwarranted threat is actually in the process of being realised would the launching of ‘pre-emptive’ war be justified; and in this case there was none. It is not justified to initiate a ‘preventative’ war simply because one fears that an enemy might attack. War is far too destructive and hazardous a business to launch on simply speculative grounds.

Therefore, it is not accurate to claim like Dillon, or imply like Newton, that Grey and his supporters wanted Britain to join France and Russia in launching an aggressive war against Germany, simply to counter the threat of her rising power. Certainly, the British were worried by that rise and especially by its unpredictable, aggressive swagger under Kaiser Wilhelm II, and they sought to contain it. Nonetheless, their realpolitik was disciplined by moral and legal considerations. Basic to their justification of British belligerency was that France should have suffered unwarranted attack. And were Germany to make that attack by invading Belgium too, then moral justification would acquire legal force, since Britain was a guarantor of Belgian neutrality by international treaty.

Certainly, Britain’s national interest in her own security was also engaged. The Belgian coast faced London and the Thames estuary, and so it had long been British policy to keep that coastline free from hostile control and the threat of invasion. It is true, therefore, that, in seeking to bring Britain to the defence of France and Belgium, Grey also sought to forestall German domination of north-western Europe. Not all national interests are immoral, however, and this one is unobjectionable. What is morally crucial is that Britain did not help to initiate a preventative war to maintain a favourable balance of power.

Germany had suffered no injury, nor was she under any emergent threat of suffering one. Unprovoked and on a fabricated pretext, she launched a preventative invasion of France and Belgium to establish her own dominance. In response, Britain went to war to repel an unjustified attack on a neighbouring ally, to maintain international law, and to forestall a serious and actualised threat to her own national security. She was right to fight.

In sum, Douglas Newton’s book is valuable in two respects, one intended and the other inadvertent. The Darkest Days lays out in unequalled detail, and with some dramatic verve, the British cabinet’s fraught deliberations in the fortnight preceding its fateful decision for war on 4 August 1914. In so doing, it also lets us hear again the many eminent voices that argued fiercely for Britain’s neutrality.

At the same time, however, Newton’s complete failure to achieve any charitable understanding of Grey produces a portrayal so relentlessly hostile as to be prima facie implausible. It also prevents him from making the morally crucial analysis of the conditional nature of Grey’s commitment to France. In this case, therefore, the author’s prejudices have done some violence to the data. But at least Newton’s candour lets us see it.