Working in the archives of the Imperial War Museum in London always gives me the visceral anticipation I had as a child at Christmas. A catalogue search gives a brief overview of the subject matter in a file, but it is not until the box is laid on your desk, and you undo the neatly tied bow of archival tape and see the contents that the process of discovery begins.

The Morris diary file, Diary of a Wartime Nurse, unexpectedly rewarded me with a hefty 300 or so pages of typescript waiting to be read, quite remarkable when I had found no other second World War nurse’s diary that was so complete, taking the reader right through the war and its aftermath.

Moreover, nothing in the catalogue description had indicated that Mary Morris was Irish, so the reading was a further act of discovery – a hint when she mentions her accent and family in Ireland in a couple of early entries, but nothing else until she is on the boat train to Holyhead on her first leave, and then seasick on the ferry, excitedly meeting her cousin Tommy at Dún Laoghaire, and, after a large unrationed breakfast, trundling across the country to her local station, Woodlawn, where her “Auntie”, who brought her up after the death of her mother when Mary was three weeks old, is waiting with the ass and trap. So not only does the diary give us a first-hand account of a nurse at war, but interweaves this with a particularly Irish perspective.

Reading a diary is to enter into the private, spontaneous thoughts of its writer. In wartime, private thoughts and feelings are of necessity inseparable from the larger public events. In Mary’s diary each documenting of the personal exists in the context of those historical moments with which we are so familiar: the Battle of Britain; the Blitz; the D-Day invasion.

Immediately likeable and sympathetic, her first entry begins with the terse “The real war started for me today”, but almost immediately admits us into the vulnerability of the lowly probationer: “Staff Nurse Jones reduced me to tears twice before the 9 a.m. break”. Yet as her ward fills with wounded evacuees from Dunkirk, any self-pity quickly turns to empathy as she describes the “severely burned” Brian Mullins who is “about eighteen years old – my age” and needs “morphia every three hours”.

Alongside this characteristic empathy we also find the Mary who daringly defies hospital rules, accepting a dinner invitation from a soulful French soldier-patient, Pierre, “with beautiful brown eyes”. When caught she faces the matron’s wrath, and in spite of her fear of dismissal gives a wonderfully irreverent description of her in “starched cap with frilly edges and a large bow tied under the medley of chins, all of them voicing disapproval”, as she is reprimanded severely for being “far too flighty”.

Mary is anything but flighty, and it is thanks to an innate unwillingness to adhere to the rules that we have a diary from her time on active service, the keeping of which was forbidden. As she writes later, “I have never been much interested in rules unless there is a good reason for them.”

The critical intelligence she brings to her desire to bear witness means that she consciously records events that others might prefer to forget, such as the starvation deaths of young German POWs of the British who are brought to her hospital in Louvain in December 1945: “This little episode will be covered up very nicely, nothing of it will reach the newspapers or the people at home”.

In Normandy she observes the friendship between allied and enemy patients as they help each other out, calling her ward “neutral territory”, and wondering why “they are all tolerant of each other inside this canvas tent, and killing each other outside”. She is thoughtful, sharply observant, witty and resilient.

A sense of humour emerges in some unexpected places, such as when she recounts disembarking onto the landing craft as she and her fellow nurses follow in the heels of the D-Day invasion: “The sailors had attached a scrambling net to the side of the ship and in theory we were to descend in agile fashion down this net. ... The men on the landing craft were ready to catch us as we jumped aboard. That was the theory, but heavy seas made the synchronisation of these events highly unlikely. ... I kept going down with the Mae West bulk constantly pushing me away from the too-mobile scrambling net. I thought I was almost there when a voice behind me said ‘Hold on until the exact moment I say and then jump backwards’.’’

In spite of the suffering she witnesses throughout the war her diary entries show a young woman who retains an intrinsic love of life that allowed her to survive the long years of emotionally and physically exhausting work.

The diary’s importance lies not just in Mary’s story alone, but also in the stories of others that she weaves into her daily entries. Thus we learn about the chaos of the Battle of Arnhem in the words of the men who are brought to her hospital: “Sgt Mullins . . . described that awful eighth day at Arnhem as chaotic fighting, groans and shrieks of pain, heavy gunfire, the dead lying all round us. The wounded screaming for water and stretcher bearers, machine guns everywhere, trapped between German infantry with mortars behind and half-track tanks in front.”

Even in wartime life is not all suffering. Mary retains a sense of fun, enjoying much male attention at parties and dances as a welcome respite, and reminding us of the youth of those who always carry the burden of war. But even as the war brings people together, it disrupts the continuity that could allow close relationships to develop – units move on, men return to the various fronts never to be heard from again: “One wonders, have they been killed or just posted to another theatre of war?”

For Mary, a chance wartime meeting will ultimately bring her to make her home in Britain, and this decision may well have had an impact on the survival of the diary. Without the Imperial War Museum as a repository and without the British context which viewed this experience as important, it might have been lost. The Ireland of the 1970s, when she had the diary typed and submitted it to the War Museum archives, had not reconciled its history to the point of embracing the experience of those Irish volunteers of whom Mary was one.

On a first reading I was sure this diary would have a broad appeal, and the most rewarding thing about participating in its publication is that with the generous support of the Morris family I have been able to make it generally available. Mary’s vivid writing made its editing a pleasure, and only repetition or inconsequential events were omitted to bring it to a manageable size.

The publication of this diary, in a special Irish edition, along with recent accounts of Irish participation in the war by historians such as Richard Doherty, Mary Muldowney and Steven O’Connor, has further historical significance. It will, I hope, bring to light more such accounts, long hidden, perhaps, in attics and storerooms, so that stories that have been silenced will now be given a public voice, and it may encourage those who participated in the war to tell their experiences to a country now eager to listen.

A Very Private Diary: From Galway to D-Day by Mary Morris, edited by Carol Acton, is published by Orion, priced £14.99