When Scotland’s national poet travelled to Nigeria to ask her birth father if he ever thought of her, he said no. Does it hurt to put this on stage? And should the next ‘makar’ be on £30,000?

Before Jackie Kay was a writer, she was a character. “When you’re adopted,” she explains over lunch in a Glasgow cafe, “you come with a story.” Her adoptive mother Helen – fascinated by her possible origins – encouraged young Kay to speculate about her birth parents. It was known that her father was Nigerian, her mother a white woman from the Scottish Highlands. Were they, perhaps, torn apart by racial prejudice in 1960s Scotland?

There was tragic romance to that idea, and a fairytale quality in the notion that Kay, offspring of forbidden love, should come to live with John and Helen, two people who had plenty of love – not to mention songs and stories – to share. Little wonder that Kay has come to think of herself as a creature not only of genetics but of the imagination. As Scotland’s national poet writes in her beautiful memoir Red Dust Road, she is “part fable, part porridge”.

Red Dust Road, adapted for the stage by Tanika Gupta, is to be presented at the Edinburgh international festival. I catch some scenes in a National Theatre of Scotland rehearsal room: Stefan Adegbola and Sasha Frost are running through the moment when Kay, visiting Nigeria, meets her birth father Jonathan. “Did you ever think of me in all those years?” Frost asks. “No, of course not,” Adegbola replies. “Why would I? It was a long time ago.” This exchange feels brutal, but Kay looks on impassive. She lived it.

Kay is 57 with a strong, theatrical energy. Joy, the name she was given by her birth mother, suits her. There is, though, a darkness, too. She has written of “a windy place right at the core of my heart”. How does she feel about Red Dust Road becoming theatre? “It’s exciting but I underestimated how difficult I would find it,” she says. “I’ve found the process challenging because it comes at a hard time in my life. My mum is about to go into a care home for a while, and my dad’s quite frail.”

Facebook Twitter Pinterest ‘I used to not feel at home’ … Kay as a child in Scotland.

John Kay is 94. He read the first 20 pages of the Red Dust Road script and handed it back with the words: “Jackie, I cannae read any mair. I’m saturated in my ain life.” His daughter feels the same. Yet she has returned again and again to her own story. Her first poetry collection, The Adoption Papers, written in the 1980s before she had made contact with either lost parent, imagined her biological mother’s voice. “I gave birth to my birth mother,” says Kay with a laugh. “How creepy is that?”

Red Dust Road, more than 20 years on, told the story of her search for her parents. Her most recent book, Bantam, contains two poems about her birth mother, who died in 2016 and whose name was Margaret – but in Red Dust Road, she is referred to as Elizabeth. Kay attended the funeral and read two poems: one during the service, another at the graveside. It was a difficult experience. She was introduced as the national poet of Scotland, she says, but not as Margaret’s daughter. “I found that very hurtful, but I will get over it. There’s no point in holding on to rancour and bitterness.”

Although she built a relationship of sorts with her birth mother after meeting her for the first time in 1991, she only ever had that one meeting – in 2003, in an Abuja hotel – with her biological father. The scene, as she recreates it, is tragicomic: Jonathan is a born-again Christian who preaches and dances and sings at her, stopping only to ask her inappropriate questions about her lesbian relationship: “So how do you have sex?” Kay had hoped that they would meet again, but he refused. They are not in contact, although she is in touch with his sons, one of whom is coming to see Red Dust Road.

Scotland is 30 or 40 years behind any other English city in terms of racial attitudes and integration

I tell Kay the memoir made me feel angry, on her behalf, towards her birth father. This, she says, is a common reaction. She is not angry: to allow herself that emotion would be an acknowledgement of weakness. All Kay’s birth father ever gave her, beyond the moment of conception, was that one unsatisfactory encounter in Nigeria. But through storytelling, that moment of pain has become a crucial and brilliant scene. It feels like a rebalancing of power.

“I think that’s right,” she says. “I didn’t think of it as revenge. In a deeper way I am taking something from him. To write about somebody without their complete permission is perhaps like some people believe of photographs: taking a little bit of their soul. I agonised about the ethical challenges. But I think I have a right to tell my own story.”

Since 2016, Kay has been Scotland’s makar, a position akin to poet laureate. “It’s a fantastic gift,” she says. “It gives me a chance to record our history at this hugely important time politically.” Her tenure will end in 2021. The appointment is made by the Scottish government and Kay intends to argue that her successor should be paid £30,000 annually, in line with that of Ireland’s professor of poetry. “I think it’s really scandalous to pay your national poet five grand.” This isn’t a personal complaint about what she earns, she wants to make clear. She feels honoured to have the role. But it can be demanding and ought, she feels, to be properly remunerated.

Facebook Twitter Pinterest ‘It’s a fantastic gift!’ … Kay celebrates becoming Scots makar with Scotland’s first minister Nicola Sturgeon in 2016. Photograph: Andrew Milligan/PA

In a recent poem to mark the 20th anniversary of the Scottish parliament, Kay wrote, “I used to feel a foreigner in my own land / I used to not feel at home.” Growing up in Bishopbriggs, on the edge of Glasgow, she experienced racist abuse, verbal and physical, and felt she had to leave Scotland for London and then Manchester (where she and long-term partner Denise both have their homes) in order to gain confidence and opportunities.

She feels the country still has a long way to go. “Even though there’s a massive amount of people of colour now living in Scotland,” she says, “this country is 30 or 40 years behind any other English city in terms of racial attitudes and integration. There’s no proper acknowledgement of the slave trade and how many Scottish cities were founded on money from that. Our children are just not taught that history.”

For the last four years or so she has spent most of her time back in Bishopbriggs – in the same house she was brought to as a five-month-old, looking after her parents during the day and writing deep into the night. Red Dust Road is a love letter to John and Helen Kay: communist activists, world travellers, jokers, free spirits, singers of jazz and protest songs. In their daughter’s work, they are heroic, almost mythic figures (“I’m in awe of them still”) and she feels a duty to record their lives.

Helen is 88. She has been in hospital for the last few weeks. John is too frail to visit, so Jackie conveys videos and love letters back and forth. She shows me, on her phone, the actor Elaine C Smith, who plays Helen in Red Dust Road, visiting her in hospital, the pair of them singing Pete Seeger’s If I Had a Hammer and Cole Porter’s Brush Up Your Shakespeare, two classics from the Kay family repertoire. Smith has known the Kays for years; John used to be on the board of Wildcat, the popular political theatre company of which she was a part.

Facebook Twitter Pinterest ‘I owe my parents my life’ … Kay. Photograph: Murdo MacLeod/The Guardian

Was writing Red Dust Road, in part, a way of making her parents immortal? “Yes, it’s a way of not letting go. That’s probably why I’m finding the rehearsals so difficult.” On the page, her mother and father are fixed and vivid in their vitality; in real life, that can never be so. She has become the parent. Her dad, tucking her in at night, would say, “Courie in, courie in” – courie being a Scots word for snuggle. Now she says the same “and I kiss his wee papery forehead”. They all adore each other. “I owe them my life.” They chose her and now she chooses to care for them.

Recently, visiting the home where John and Helen might both live, Jackie had a conversation with a nurse. She had not yet met the Kays but, seeing their daughter, assumed that they were a black man and white woman. “Aw,” the nurse said, “I thought I was going to get my first mixed-race couple.” Well used to people making assumptions about her background, Jackie explained that, no, her mum and dad are white and she was adopted. Then she went back and told her parents. They, in their generous way, saw the humour in it.

“You should have told her we are a mixed-race couple,” John laughed. “I’m from Glasgow and she’s from Fife!”