Helen Castor, 56, is an academic, author and broadcaster whose acclaimed books include She-Wolves: The Women Who Ruled England Before Elizabeth and Joan of Arc, both of which she also presented as television documentaries. She is a fellow commoner at Sidney Sussex College, Cambridge. Her new book, The Eagle and the Hart: The Tragedy of Richard II and Henry IV, explores political rivalries and the most audacious coup of the 14th century. It has been described as a “dazzling tour de force of epic royal history” by Simon Sebag Montefiore and a nonfiction book of the year by Andrew O’Hagan.

What drew you to the story of these two men?
It encapsulates everything I love about medieval history. I’m interested in power and how it worked in an age where you’ve got no standing army, no professional police force, no modern communications – how does a government in Westminster rule a whole country? You’ve got these two individuals – first cousins, almost exactly the same age but such utterly different men – brought to the point where the failings of one mean that the other has to take over, causing a whole different set of problems. If you wrote it in fiction it would look too neat. And of course the fact that Shakespeare has told their story so gloriously is a whole other layer drawing you in.

It’s a real psychological drama – tell us about Richard and Henry.
Richard becomes king at 10, and for as long as he can remember has known that he is the one chosen by God. He’s wrapped in cotton wool and told that the future of England depends on him. Henry is his father’s only legitimate son, but he is brought up knowing that he’s got to learn how to do the job. Richard grows up cossetted, whereas Henry is pushed to learn all the skills he’s going to need as the greatest nobleman in England. The theory is that he’s going to stand at Richard’s right hand and help, but of course that’s not how it works out.

How much has our view of this episode been coloured by Shakespeare?
Hugely. I’d argue that Richard II has a claim to be Shakespeare’s greatest play and at its heart is this examination of kingship and humanity. I think one of the problems is that the Shakespeare character is so thoughtful and his ruminations on what it is to be a king unmade so powerful. If the real Richard had been half as thoughtful it might not have been as disastrous a reign. But I also wanted to bring Henry forward and allow him to stand right next to Richard, to see both of them as fully as we can.

Why is this story so resonant now?
Because we’ve been able to see narcissism in a political leader, and the potentially destructive and appallingly difficult effects of that playing out. I’ve been working on this book over the past five years and it has been extraordinary in that time to watch what happens when a leader is so consumed with the idea of power and authority as their own right that they are willing to attack and indeed break not only rules but the rule of law and constitutional structures rather than be thwarted. I’d rather not live in such interesting times, but the resonances are extraordinary.

How do you approach writing a history like this – is it different from your academic work?
Narrative is the key for me, and this is the key step away from the kind of history I was writing when I was teaching in a university. What I want to do is stand in the shoes of the protagonists in my story, try and see through their eyes, so chronology becomes absolutely crucial, instead of the rather eagle-eyed academic overview where you’re trying to analyse structures and processes.

You were a Booker judge in 2022. Have you always been an avid reader of fiction?
Yes, but I don’t do it enough. You won’t be surprised to learn that I love historical fiction, especially Hilary Mantel’s work, and I also love William Golding’s The Spire, that creation of a very particular medieval world. What I loved about [the Booker] was it meant reading 168 novels in seven months – I enjoyed the intensity of it and the chance to read a snapshot of extraordinary fiction from one year. We all loved our shortlist, and if you’d asked each of us to name our own winner, I suspect you’d have ended up with five different titles. The prize went, in the end, to the book we could stand behind together [The Seven Moons of Maali Almeida by Shehan Karunatilaka], which felt entirely right.

Was there a book or author from your childhood that made you want to be a writer?
Jean Plaidy’s books about Mary Queen of Scots and Elizabeth made me want to be a historian. I think for the past 20 years I’ve been learning to accept and say out loud that I do want to be a writer, and one of the reasons I’m very slow at writing my books is because every sentence, every paragraph – that process of getting the prose right matters as much as anything else to me. My husband’s a poet and we end up talking a lot about the middle of the Venn diagram where the way we think about writing meets – the rhythm of a sentence, the feel of a line.

Which modern historians do you admire?
Too many to list – I often read with a combination of awe and envy – but I do always write down sentences that ambush me with some combination of gorgeously lucid language and sharp wit. Recent names in my notes are Tim Blanning, Jessie Childs and Edward Wilson-Lee.

What would your readers be most surprised to find on your bookshelf?
I don’t know if it’s surprising, because to me it makes perfect sense, but I love science fiction. Growing up, one of my favourite books was I, Robot – Isaac Asimov’s collection of stories, and I loved John Wyndham. I think the connection is that thing of creating worlds, and seeing how human beings react in a world that might be unfamiliar to us now but has its own logic and its own culture, so I see them as very connected.

Which book or writer do you think is most underrated?
I don’t know why Diana Wynne Jones is not hugely bigger than she is – the scope and richness and depth and scale of her writing has always astounded me, and it feels as though she’s still somehow a best-kept secret. When I started reading her as a child, young adult fiction didn’t really exist as a label. She should be a name in every household and I’m not sure she is.

Which book do you wish you’d written?
A Place of Greater Safety by Hilary Mantel. I remember vividly where I was when I finished that book and I have never got to the end of a book that is getting on for 900 pages wishing it wouldn’t stop.

What next, after five years on this book?
The next book is going to be about Elizabeth I. Given that she once said, “I am Richard II, know ye not that?”, it is a fantastically interesting transition to make from the 1390s to the 1590s. She’s a scary prospect, but she’s fascinated me since I was tiny and she’s a brilliant and compelling and perplexing character to spend time with.

What do you do when you’re not reading or writing?
Music (one day I will learn to play bass). Friends. Liverpool Football Club. Watching my son row, a sport about which I knew nothing when he started, but now fancy myself an armchair expert. My husband lives on a different continent so, when we’re not together, talking to him is the heart of my day.