During July and August 1914, people around the world watched apprehensively as the global crisis that would become the First World War took shape. While to some it was clear almost immediately that the assassinations of the Archduke Franz Ferdinand and his wife Sophie in Sarajevo would provide the spark in the tinderbox that many observers had been expecting for years, it took weeks for the framework to emerge, for alliances to settle, and for the war to become a fact.

More than most, Brooke had access to well-placed individuals – Edward Marsh, and Violet and Cynthia Asquith – with some insights: ‘Everyone in the governing classes seems to think we shall be at war’. Friends with any real political responsibility were run off their feet, meaning that Brooke saw out the final days of July in a state of heightened and semi-ignorant anticipation. Rumours spread quickly and were consumed voraciously by a tense citizenry. In cities, towns, and villages nervous crowds gathered, waiting to hear the news as telegrams flashed between European ministries. Marsh, who was virtually sleeping at his desk, was too busy even to write. He eventually stole a moment to send a message to Brooke, noting wryly that this silence ‘must have brought the reality of war home to you more than anything else’.

On 1 August, Germany declared war on Russia, and the mood shifted. On the same day Brooke wrote to Jacques Raverat, wondering ‘what can one do if there's war?’ On 4 August, Britain declared war. He later described the moment he, and fellow Londoners, found out for certain that the period of speculation was over: