Between The Crosses is not what I'd call a play. I'm not sure exactly how I would describe it though: a lecture perhaps, or an annotated memoir, or a live version of Who Do You Think You Are?, maybe. Alone on the stage, actor Will Huggins plays a recording; it's his real-life great-uncle Edgar's voice, being interviewed by the Imperial War Museum about his experiences of the First World War. Breaking into the recording, Huggins offers explanation and context for the story we're hearing, and shares a few thoughts and observations of his own.

The opening 15 minutes are the most overtly lecture-like – and here, I'm afraid, I found Huggins' forced enthusiasm exquisitely annoying. "How the First World War starts is something we should quickly look at," he brightly announces, before rattling through the history far too fast for anyone to actually understand. It's intended to be grimly humorous, complete with emphatic hand gestures and comedy foreign accents, but it felt a little too facile and childish for such a serious theme.

Yet the energetic style comes into its own before long, when we learn of Edgar's march through Ypres and the bloodshed that soon followed. The storyline here is confusing because the battle was confused; Huggins' frenetic delivery captures that sense of chaos, while carefully keeping the key facts clear. He illustrates his narrative by chalking an ever-changing map onto a giant blackboard, and there are moments when sharp reality comes through – when he rubs out the name of a dying soldier, or crosses through a count of 1,000 men and chalks up just 200 who survived.

In a repeated highlight, Huggins draws ironic contrast between cheery official reports and the evident reality of Edgar's life. Less predictably, and more interestingly, Edgar's recorded voice sometimes departs from the narrative we're expecting – most notably, when he says that he doesn't actually recall being shot at. Huggins makes it clear that he doesn't believe this, and those same official accounts do seem to prove that Edgar's memories are selective ones. But I still found the treatment a little discomfiting – especially when Huggins calls on his own very different experiences to try to explain the gap.

I think there's exactly the wrong amount of Huggins' own voice here. He pushes himself forward every now and then, advancing an argument about why Edgar might have left some of the details out; but then he steps back, never developing those thoughts well enough to make them sound more than speculation. There are simpler explanations, like modesty or a healthy desire to move on, which Edgar himself might have reached for. It felt a little rude to psycho-analyse a man who seemed, through the recording, to be very much present in the room.

But I can't deny that Huggins asks some thought-provoking questions, and – just as important – offers crucial insight into the incomprehensible reality of war. Between The Crosses is a work in development, and when the whole thing's working as well as the best parts, it'll be a fine and striking addition to the canon of centenary memoirs. At the end, Huggins shares his applause with the recorded spirit of Edgar; and it's right that he should. For Edgar is the second performer here, and it's Edgar's story that deserves to be kept alive and told.