Reading his own specially commissioned poem to a crowd of 20,000 people gathered to commemorate the centenary of The Somme was an occasion Lemn Sissay will never forget, perhaps the defining moment of his career. “That stands out above and beyond everything else. I was very proud to be there,” he accedes.

But there have been many to choose from; his MBE, meeting the Queen, being appointed Chancellor of Manchester University, being commissioned for the 2012 Olympics, making BBC documentaries, being published, the list goes on. “I know, I’m an under achiever,” he laughs.

What makes Lemn Sissay’s story even more inspiring is that he achieved all of these things, despite his terrible childhood.

The 49 year-old’s story is a harrowing one, his tale of abandonment, adoption, care homes, neglect and rejection enough to bring even the strongest child to its knees.

And yet here he is enthusing about coming to the Woodstock Poetry Festival next week, organising care leavers' Christmas parties, travelling the country to recite his poetry to crowds, big and small: “I get a real kick out of it, whether it's to two people or 20,000 people and I get so much from it. Besides, if it doesn't mean something to you it wont mean anything to them."

Yet one is unable to write about this great poet without outlining his childhood experiences, ones he draws on extensively throughout his work.

Those of you who heard him on R4s Desert Island Discs recently with Kirsty Young will already know the story, but for those of you who didn’t, Lemn was given up for adoption as a baby, fostered by a Lancashire couple whom he called mum and dad, and then placed into care aged 12 where he remained until deemed old enough to fend for himself. He was given his birth certificate on his 17th birthday and discovered his real mother was Ethiopian.

By this stage he had pledged to achieve three things – to write poetry, find his birth mother and uncover what happened to him. That he has achieved all three is truly extraordinary and a testament to the determination of Lemn even as a young man.

That he went onto achieve such monumental success in the world of poetry is quite another, regardless of his shaky start.

The 49 year-old was sent his official documents 10 months ago and discovered that his foster mother had suffered from post natal depression after the birth of her own three children and had severe financial worries.

“I was the fall guy but I didn’t see it coming. Imagine telling any 12 year-old they have to go into care. But I can see it all now, and all families have their problems. I learned that adults can make big mistakes and that it wasn't my fault. The social work files back that up. They say I hadn't done anything wrong.”

While others would have turned to drink, drugs or self-harming, Lemn turned to poetry, a cleaner at his care home remembering how he was always scribbling away in the corner, in a subsequent BBC documentary.

“I wouldn’t have got through it without the poetry. It allowed me to have a freedom away from the madness of the care system. It gave me an acknowledgement of my emotional state and helped me make sense of it all.”

Where did this poetic streak come from I wonder? “I don’t know. I haven’t found any obvious creatives in my family during my research. But I knew, with an unquestionable certainty, that I was going to be a poet, from the age of 12.

“But then if you want to find out how a child in a care home is feeling don’t write an evaluation, get them to write a poem, or a song, or paint a picture. Because poems are always truthful."

His positivity certainly helped Lemn survive his own childhood, that and his ability to forgive the adults in his life who let him down. But more than anything, his innate need to write poems is, he thinks, what has ultimately kept him sane.

“Many children in care homes think it is their fault that they are there. It was good to discover it wasn't mine. And I have learnt to forgive my foster parents and in so doing have moved on. Because until then I was carrying all this anger around with me."

Having traced his Ethiopian birthmother working for the UN in The Gambia, their relationship didn’t work out as he’d hoped, Lemn embodying his father too much in looks and age apparently. “It is complex,” he says simply. During a documentary about tracing his father, he then discovered that he’d died in the 1970s but that he was very like him.

Lemn has no children of his own, having just split with his partner of 13 years, and while he keeps ridiculously busy, there is still a vulnerable side to him – his poetry telling you more about the man than any psychiatrist.

When I ask whether he ever reflects on his achievements he says no, because that’s what a family is for, as if all of his achievements are hollow without one – and that regardless of all his hard work, part of him will never heal.

And yet Lemn is such an inspiring, cheerful, interesting, driven man, with a ready laugh and an honesty that sometimes takes your breath away.

Sharing the intimate and painful details of his life doesn’t worry him in the slightest either. "My childhood is a public record anyway. I have the files, so for me speaking out abut the truth doesn’t worry me. It’s part of who I am. And I don’t feel as if I’m exposing myself. It has always felt right to talk about and share my story. I needed to answer a lot of my own questions, and no one else was going to.

So who taught him to love words then, school? He splutters, "Absolutely not. I taught myself. I read a lot. The Caribbean poets inspired me."

And then he laughs: "I thought I was Caribbean. I grew deadlocks and everything,” he laughs. “And then I found out I came from Africa. But then I've lived my life backwards in many ways, proving my family existed came first when everyone was out working and getting jobs, and I wrote poems to pay for that journey.

"But I still don't have the same context as other people and that’s the truth. I have never had a family to come home to, someone to say 'well done'. So yes it has affected me but it didn't crush me. The most important thing is to do the best I can.

"And it has taken a long time to get to where I am now and have learnt that the most important thing is to be kind to yourself, because we all struggle, and to relax.

Does he? “I’m not very good at it,” he laughs, getting up to go and write his next piece of work, a commissioned poem. “I need to work on that. On the other hand perhaps I just need someone to say ‘oh shut up and put the kettle on.’

And with that he’s off, leaving that poignant, self deprecating and insightful line floating in his absence, saying it all.

Lemn Sissay will be appearing at The Woodstock Poetry Festival 2016 which runs from November 11-13