Caroline Lucas, joint leader of the Green party and MP for Brighton Pavilion, was working on a Renaissance literature PhD when she decided that politics, not poetry, was the life for her. Michael Morpurgo had a job as a primary schoolteacher when he realised that storytelling was where his talents lay. Now 73, he is one of the biggest names in children’s literature, a former children’s laureate and the author of more than 100 works, the most famous of which is War Horse, adapted by the National Theatre into a smash-hit play and later an Oscar-nominated film directed by Steven Spielberg.

The pair meet in Lucas’s cosy parliamentary office in the House of Commons, on a day when Morpurgo has come up to London from his Devon home to visit his old primary school. Lucas used to read Morpurgo’s books to her children, while Morpurgo is a supporter of environmental causes, and with his wife set up the charity Farms For City Children. They begin by reminiscing over cups of tea about their only previous meeting, at a literary festival in Sussex, where they appeared on stage together.

Caroline Lucas The marquee wasn’t very waterproof, and you sang. The event was about war and your voice is still going round in my head.

Michael Morpurgo I won’t sing now: don’t look at me like that.

CL But it was so moving. It was that song from War Horse, Only Remembered. That tune often goes round in my head, actually.

MM I rarely talk to politicians, you know; sometimes I have found it fruitless. I think one of the problems we’re living with now is that a lot of people can’t engage with politics. I write stories and try to get my ideas across in that way.

CL Have you written any stories about politicians?

MM No, but I’m often dealing with the same issues, whether it’s migrants or war. I’ve been on that Jonathan Dimbleby radio programme [Any Questions], but you get so disillusioned. There was a perfectly nice guy on the panel – I think it was his first time – and he had a pile of notes that were clearly full of instructions about what he could say. And he was struggling, because the questions from the audience are never what you expect. I liked him, but he was put in this position where he could not say what he felt, and I thought: what is the point? You haven’t come to do a party political broadcast. Of course, on these things I’m always the odd one out – the writer, the outsider – but you can’t have a conversation with people who don’t mean what they say.

I want to tell you a story about the Guardian. Years ago, someone wrote a horrible review of a book of mine, and [adopts a stage whisper] I’ve never forgiven them. It was the book after War Horse, and someone wrote a review that was so hurtful and quite unexpected.

CL That wasn’t Private Peaceful?

MM No, it was called Twist Of Gold and it was a story about migration from Ireland to America during the potato famine. I love that book, and much more since it was attacked. It’s like attacking one of your children, and you’re like, “Keep off, that’s my baby.” Anyway, I’m not bitter.

CL I last saw you before I was elected co-leader of the party. You were talking about politics, and I just want to say that what we are doing [job-sharing] feels so positive. It’s about modelling a different kind of politics, which people often talk about, but we wanted to demonstrate that you could actually do it.

MM It lets you live a life, I expect. And many of your constituents will be job-sharing or doing the juggling that people do now.

CL I do think this place [the House of Commons] would be improved by having a few more people in it who are more grounded in the reality of everyday life.

MM If we’ve learned anything in the past few months, and I’m not sure we have, it’s that the separation between political structures and ordinary people is widening. We’ve got this huge gulf now between those in control and those being controlled. That was what the Brexit vote was about. There is this resentment.

Yes, the EU has become a bit of a monster, but I mean, what world are people living in?

CL I agree, and I don’t think it’s too far-fetched to make a link to our electoral system, because first-past-the-post enables MPs to ignore a huge number of their constituents, all the time. If you’re in a safe seat, you don’t need to care what they think because, barring a revolution, the same party gets back in time and time again. What was interesting about the EU referendum was that people were so surprised their votes had made a difference.

MM They counted.

CL Yes, and now it’s our responsibility to try to understand what was behind that result.

MM The referendum should never have happened. It was political manoeuvring on the part of the Tories to sort out their own problems.

CL It feels to me like a betrayal of young people who, by and large, voted to stay in Europe. I was very involved with a group who were using social media to try to get some different messages out there, about how extraordinary the European Union is.

MM The problem is, everyone takes peace so much for granted now, but that was the idea, originally. Yes, it’s turned into something else, and that something else has become a bit of a monster, but instead of staying and working things through, we’re going to do this thing called sovereignty. I mean, what world are people living in?

CL The English, in particular, are still struggling with a sense of identity after colonialism. We used to have a much clearer place in the world. I think trying to create a progressive patriotism has never been more important.

You won’t remember this, I’m sure, because my two boys are now 20 and 23, but when they were younger, they absolutely loved your books. We read them all the time. When my elder son Theo had to do a project that entailed writing about a book, he decided to write to you. And you sent a reply that was so beautiful, and Theo thought it was so amazing that this great author had written to him, that he said, “I’m going to write to him again.” I tried to persuade him not to, not to push it, but he did – and he got a second letter back! So you were a hero for many years in our household.

MM Well, I voted Green for the first time last year, largely because of you.

CL Good.

MM I noticed your rise – it was a quiet rise, and I like quietness. And I like people who argue with reason, and a degree of empathy and understanding of what the other side is saying. I think you never say a word you don’t mean, and there aren’t many politicians like that.

CL Thank you!

MM I moved out of London when I was little. My parents moved us to the coast of Essex, near a place called Bradwell, which is about to become another nuclear power station, and I had my first, wonderful experiences of nature there. The sea wall went past a chapel, and there were lovely fields where the hares would play, and sea birds, and the great soupy brown North Sea rolling in.

The first environmental issue I ever confronted was the plan for an atomic power station to be built there in the 1950s. Of course, the village was divided: my family’s side of the argument was that it would devastate the local area, but we lost, so my parents moved us away. It was like an Agatha Christie village: there was a squire and a policeman. They didn’t kill each other, but it was one of those essentially English places. That was where I first confronted the question of how we look after the environment, and the first time I saw adults get cross with each other.

We’ve got a large, adult, urban population who have never dug up potatoes or seen the worms wriggling

CL My political journey started with the anti-nuclear campaign. Greenham Common was really important to me, and Jonathon Porritt’s book Seeing Green was a real lightbulb moment – one of those books that change your life. It’s up to each person to decide how they can make a difference. I was living in a bedsit in Clapham at the time, and I noticed the Green party was based on Clapham High Road. So I took this as a sign and marched off and signed up there and then.

I think it’s so crucial what you’re doing with Farms For City Children, because people won’t protect what they don’t love, and they won’t love what they don’t know. That sense of getting the earth under your fingernails is crucial – it worries me so much that young people are growing up without that access to nature. I was at a conference recently, and one speaker was saying that, in one children’s dictionary, the words conker and bluebell had gone and been replaced by chatroom and blog, and that really crystallised something for me.

MM We’ve got a large, adult, urban population who have never dug up potatoes or seen the worms wriggling. The writer I grew up with, more than anyone else, was Robert Louis Stevenson, who wrote about landscape wonderfully well. But the book that is most important to me on this subject is by a Frenchman called Jean Giono. It’s a very short novella called The Man Who Planted Trees, about an old shepherd living in the hills of Provence. A visitor comes along, a student travelling around, and the old man says, “Do you want to come with me while I do the sheep?” And off they go. The old man takes a sack of acorns, he doesn’t say anything – there’s hardly any dialogue in this book – and he wanders off with the sheep and starts planting acorns. The student goes away, the first world war comes along, and when he comes back from the war, he decides to go and see the shepherd. Ten years later, the shepherd is still there, and all over the hillside are these green shoots: it’s a glorious story.

Facebook Twitter Pinterest Morpurgo: ‘I voted Green because of you.’ Lucas: ‘Good.’ Photograph: Antonio Olmos/The Guardian

CL Donald Trump’s election is terrifying from an environment perspective. If the US really were to withdraw from the Paris agreement... I mean, the irony of that, when it’s just been ratified! It would be enormously damaging. Having said that, I do think there’s enough momentum now. Countries including China are moving in a more environmentally sound direction, because they recognise that is where their best interests lie. Places like California are really roaring ahead in terms of renewable energy. It’s important to try to be hopeful, even at times like this.

MM I have a strange hope that Trump fulfils the promise of most politicians, by not keeping his promises. The problem is, he could do a lot of nasty things and millions of people would like him to, because it’s cocking a snook at liberals.

CL But some people must have voted for Trump in spite of, not because of, his racism, misogyny and climate denial – because they’re just so angry with what they see as the corruption of politics, when they see a minority of people who are doing so, so well. And we have to learn from that.

MM Because it’s our anger, too. We may not have risen to the dizzy heights of American heavy industry in the 20th century, when they were supreme. But here, too, the last coalmines have closed, and we treated people appallingly. Our job now is to educate young people, because we need them to grow up with knowledge and understanding. We’ve talked about how books have affected our lives, and sometimes they really do help point the way. We’ve demeaned our democracy, this extraordinary gift that generations fought for, and that’s what we’re handing on to our children. That’s our great crime.

I went to my old primary school this morning. I last walked into it more than 60 years ago. Then it was an entirely pink school and I was one of the pink children, and I looked around the hall today – a tiny little place, of course I used to think it was the biggest hall in the world – and I looked around and the entire world was there: every religion, every culture, and I thought, “This is extraordinary, and these amazing teachers are making it work, and this is the kind of world I believe in.” This is the world as it is.

CL I agree.

When I was at Oxfam, I remember lobbying Glenys Kinnock and thinking, 'I want to be her, on that side of the desk'

MM You’ve written a book, too, haven’t you?

CL Yes, I have, Honourable Friends. It’s a weaving together of green politics and my first five years here [in the Commons]. It felt important, watching the weirdness of parliament, to try to capture some of that. The subtitle is Parliament And The Fight For Change, and hopefully it will change, because this place is unfit for any serious purpose. We should take the refurbishment that is coming as an opportunity: let’s have a purpose-built, glass building, so people can see in. Let’s have a hemicycle, rather than a confrontational chamber that just reinforces the whole idea of shouting at one another.

MM You have to be brave to be a politician. In my case, things just happened. When I left school, I went into the army, because I was trying to work out which of my uncles I should follow. I had one uncle who was a pacifist and one who wasn’t, and I hadn’t worked out which was the path for me.

So I went to Sandhurst [military academy], where I had a strange experience in December 1962. We were in trenches and there was a fake enemy, as you have in army exercises, and they were the Argyll and Sutherland Highlanders. The people they hated most on this Earth were the English, so they were shouting across the snowy waste of no man’s land the vile things they were going to do, and I got very frightened. I realised this wasn’t for me, so I made a decision, aided by my wife, whom I married aged 19, and went to university and ended up in front of a class of children telling stories. I love what I do. When I read to a bunch of children this morning, I thought, well, it doesn’t get better than this.

CL I was older when I met my husband – 29. I’d just started working for Oxfam and I was his lodger.

MM You spoke earlier about wanting to make a difference. Of all the things you’ve done, which job has made the biggest difference?

CL I seem to feel that, wherever I go, the power is somewhere else, but I think it’s coming full circle now. When I was at Oxfam, I have a very vivid memory of lobbying Glenys Kinnock, who was an MEP and someone I respect hugely for her work on trade policy to help people in poorer countries. I saw her on the other side of the desk and I thought, “I really want to be her, I want to be on that side of the desk.” So I stood for the European parliament, and then, when I got there, it felt as if more of the decisions were being made in national governments. So I did a year’s secondment to the Department for International Development, and thought, that’s still not it – I’ve got to be an MP. Now, I hear other MPs say, “I can’t do that because the public aren’t with me.” You realise that, wherever you are, the power is with the people. Even in this place, MPs won’t move unless the public is pushing them.

MM That’s how it should be.

CL There’s something, I don’t know what the word is – not pathos, but all your books tread a line between joy and tragedy. Private Peaceful is one of my favourites. I think, for me, it was about taking your kids to a place that is potentially quite bleak, but it’s done in such a safe way. There’s a lot of grief in the books, but children really respond to it.

MM Most of them have been there. There’s been someone, a granny or a dog, it doesn’t matter. I think it’s important never to patronise children, or to think they don’t feel as deeply as we do. They’re not as informed, maybe, but they feel what we feel – and particularly, I think, they feel lonely, and books can help. Because if someone is reading to you, there is a profound engagement with that person.

Let me ask you: do you ever stand back and think, what is the point? There must be moments. Thinking of the awful thing that happened to your colleague [MP Jo Cox] who was killed not long ago, don’t you think to yourself, “Well, that woman lived to make things better, and look what happened to her”?

Once you start down the slippery slope towards despair, then what is the point? We’ve always got to feel we can fight

CL Briefly and occasionally. But what keeps you going is being surrounded by good people. I feel so blessed by the people I have working with me – it’s nearly always the case you can derive strength from that.

MM So is that what you think of, when you do occasionally put your head in your hands and sob?

CL Yes. But I also think, once you start down the slippery slope towards despair, then really, what is the point? We’ve always got to feel that we can fight.

MM That’s what I admire you for. That’s what I couldn’t do, is what I’m saying, really. As a writer, I spend a lot of time alone, which is what you must long for. But sometimes on your own you can think too long and hard about how the world is. Those moments pass.

CL I feel privileged to have met so many powerful people – I don’t mean powerful people, I mean ordinary people who have become powerful in their communities. I mean the anti-fracking Nanas in Lancashire, this group of women who have just decided they are not going to have fracking, people who have never taken action in that way before. Now I have to go – I’m supposed to be handing in a letter to the Treasury about local government cuts.

MM Can I ask you one more tiny thing? Does the history of this place, the history of people making decisions here, affect you, in the sense that you feel you are part of something that works?

CL No, it feels absolutely dysfunctional. [She smiles.] Oh, bless you. Let me give you a quick hug.

• This conversation has been condensed as part of the editing process.

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