In 2011, when Seamus Heaney announced that he would donate his papers to the National Library of Ireland (NLI), it was a source of much pride, and a little relief, for the library. There had been some speculation that the archive would go to Harvard, where Heaney had taught for many years. When the day came for the papers to be delivered, “I think the director of the library presumed there’d be a van and minions”, recalls Heaney’s son Michael. “But there was Dad carrying the boxes. He’d put them in the back of the family car and brought them round himself. It was all done very casually, but there was also a weird sense of momentousness, so much so that it felt right for us to have a drink to mark the occasion with my brother, Christopher, afterwards.”

The episode is emblematic of Heaney’s status in Ireland as a figure who is not only hugely revered for his creativity and intellect, but also loved for being approachable and down to earth. Two years later, when Heaney died unexpectedly aged 74, his family learned just how much he had meant to people, and not just in Ireland. “I was utterly taken aback by the response,” says his widow, Marie. “And I wondered whether he would have been, too. But there he was, above the fold on the front page of the New York Times, with a story about Obama and Syria down the side. It was something extraordinary to experience alongside our shock and our grief.”

Heaney’s funeral was shown live on Irish TV and the cortege was given police outriders. Mourners ranged from the Irish taoiseach and president to Bono and Shane MacGowan. “It was in effect a state funeral without the military,” Marie says. All over the country there were books of condolence and the family received thousands of letters and cards. “They all had some personal connection that they wanted to share,” recalls their daughter, Catherine. “People still come up and tell me stories about meeting him and how much it meant to them.”

Nearly five years on from Heaney’s death, the family have gathered to discuss two major events that will commemorate his life and work: an exhibition of the NLI Heaney archive in a new cultural space in the grand 18th-century Bank of Ireland building in Dublin, and the publication of a new anthology of his work, 100 Poems (Faber).

‘An affable and benign presence …’ Seamus Heaney, centre, with Christopher, Marie, Catherine and Michael. Photograph: Catherine Heaney

Surprisingly, there isn’t a single-volume selection of Heaney’s poetry. He had expressed a desire for a “really focused collection”, and an idea for 75 poems for his 75th birthday was mooted. Now the family have completed the job for him, choosing a selection that runs from “Digging”, the 1965 poem by which the son and grandson of farmers boldly announced his intention to set out on a literary career – “I’ve no spade to follow men like them. // Between my finger and my thumb / The squat pen rests. / I’ll dig with it” – to a poem written for his granddaughter just 10 days before he died.

Catherine took on the coordinating task “using a very unpoetic spreadsheet”, and 70 or so poems quickly selected themselves. “I cannot tell you how many readings I attended,” says Marie. “And while he never gave exactly the same one, there was certainly a core of poems that he returned to.” Aside from his best known work, all the family have poems written for them, from love poems to Marie to one recounting the morning Catherine was born; a “slapped palpable girl” presented to the poet. Many other less obvious poems also meant a great deal to him, and can cast a new light. “‘Helmet’, for instance, is a lovely poem”, says Catherine, “if not one that everyone would necessarily know. But it was an actual physical object in our house, which also links to 9/11 as a salute to the firemen.” The haiku “1.1.87” – which reads in its entirety: “Dangerous pavements. / But I face the ice this year / With my father’s stick.” – is in, “because we all remember the time when Dad did his knee in. He slipped on ice while in Harvard in late 1986, and for a while it was a big part of his, and our, lives. But later in the year his father died, and it was after that he wrote the poem.”

There are countless examples of how the poetry has entered the everyday lives of people Marie Heaney

While the Heaney children grew up with his work, by a quirk of the curriculum they didn’t study him at school. It was only when in the US for a semester that Catherine had the bizarre experience of having to answer an exam question about a poem written by her father about her grandmother.

Heaney wasn’t particularly hands on with his own children’s school work, but did his bit for the grandchildren. Christopher remembers him reading a Dr Seuss book. “He was really working to make it come alive, but also mouthing over to me as he read: ‘Damn bad rhyming.’ He also wanted to get his red pen out for some of Julia Donaldson’s metre.”

But he did give Catherine a few pointers about his beloved Latin before she started secondary school. The family laugh at his habitual use of Latin, and pig Latin, phrases around the house, with “sanctus fumus” (holy smoke) a particular favourite. And so it was no surprise that his last communication to Marie was a text from hospital, minutes before he died, saying “noli timere” (don’t be afraid). Michael recounted the story in his funeral address, and not long afterwards a large mural by the graffiti artist Maser appeared on the gable end of a house in Dublin. A new Maser artwork – an installation that picks up on the ideas of flight, uplift and birds in Heaney’s poetry, will greet visitors to the exhibition.

A mural in Dublin by a graffiti artist Maser called ‘Don’t be Afraid”? It was inspired by Heaney’s last words Photograph: boomingback.org

NLI director Sandra Collins says that when Heaney donated his papers he indicated he would welcome an exhibition. However, “he specifically said that he didn’t want to ‘put out Yeats’, who already has a longstanding exhibition,” says Collins. The new Bank of Ireland space, to be opened next week by the Irish president, allows for the literary titans’ work to be displayed for at least the next 10 years in their own venues. The Heaney show will be free to the public and is expected to receive 100,000 visitors a year. “He threw nothing away and his papers are already our most consulted archive.”

The exhibition combines archive exhibits and multimedia features. Visitors will hear Heaney reading “Digging” while looking at the original New Statesman proof of the poem, and the letter from Faber confirming publication of his debut collection in 1966, Death of a Naturalist. It then progresses through broadly chronological themes. “Excavation” recalls the soil, the bog and peat of Heaney’s rural upbringing, as well as the Iron Age “bog bodies” that prompted some of his best known poems.

In the “Creativity” section sits his desk from the attic office that overlooked Dublin Bay and Howth Head. Heaney described it as just “a slab of board on two filing cabinets”, explaining that he “liked the makeshift nature of the arrangement. I always had a superstitious fear of setting up a too well-designed writing place and then finding that the writing had absconded.” Manuscripts in this section include the poem “Trout”, which was literally written on the back of an envelope.

The manuscript of ‘Trout’ by Seamus Heaney. Photograph: National Library of Ireland

The section on “Conscience” sets Heaney against the backdrop of the Northern Ireland Troubles, as well as his other engagements with social justice and global politics such as “From the Republic of Conscience”, written for Amnesty, and “The Cure at Troy”, which was written with Nelson Mandela in mind. This section also reflects Heaney’s struggles with the ethical question of how does a poet properly live and write, and how to speak about things without being a spokesperson. It was a fine line to tread and Marie confirms that he “really was torn a lot of the time. He was a nationalist by birth, and by inclination, but that nationalism was being hijacked in a way he detested. He got stick from both sides, and was threatened.”

The last section of the exhibition is about Heaney as a public figure, especially after the Nobel prize in 1995, and one of the closing exhibits is a video of Croke Park stadium, where two days after his death an 80,000 crowd for an All-Ireland Gaelic football semi-final broke into spontaneous applause to mark his memory. “It is hard to think of another creative and cultural figure who had that sense of belonging to a country,” says Katherine McSharry of the NLI.

“We were all very aware other people thought they knew him as much as we did,” Catherine says. “That was the way he moved through the world. He was very approachable and friendly and genuinely focused on the person he was talking to at the time. And he managed to balance the two pretty well in that he was always just Dad at home. But in hindsight we realise how many pieces he must have cut himself up into in order to do his civic duty, his poetic duty, his family duty and everything else.”

Always an enthusiastic and expansive letter writer – and then a dogged user of fax to the extent that Faber kept an old machine in their rights department solely to receive communications from him – his writing tone changed as time went on. “They became more business-like,” says Christopher, “more and more began with an apology for his slow reply and ended with him saying he was writing from an airport lounge or was going to catch a plane the next day.”

Seamus Heaney: Listen Now Again at National Library of Ireland, Dublin, July 2018 Faber Letter Death of A Naturalist Photograph: National Library of Ireland

Marie says that he always said he was “more of a jet-sitter than a jet-setter, but I would sometimes be quite angry about the demands made on him. I saw how he was sort of frightened to go on holiday because he knew he would face sacks of mail when he came home. I felt he could have spent a lot more time at his poetry. That said, he did a prodigious amount as it was, not to mention the criticism and teaching.”

And the way his work has entered the culture remains a remarkable testimony. The Heaneys are not the only family with strong associations to these poems. There seem to be few Irish weddings at which “Scaffolding” is not read, and few funerals that don’t feature “Postscript”. Every Irish child will know “Mid-Term Break”, written by Heaney about being taken out of school when news came of the death of his three-year-old brother. “For years he didn’t read it in public,” says Marie. “Maybe because his parents were still alive. But towards the end he introduced it and I once remember him say he was going to read it, and seeing a man in the audience reach over to hold his wife’s hand. I assume they too had lost a child. There are countless examples of how the poetry has entered the everyday lives of people and some of the ways the work connects is very touching indeed.”

Although he was 74 when he died, there is still a sense that his life was somehow cut short. “So it did comfort me,” says Marie, “when I heard that Auden had once said that no true artist died before they have said what they had to say. And I think he did manage to say what he had to say.” She is also aware that Heaney’s affable and benign presence was a part of the work’s appeal, sometimes giving poetry that could be quite dark a more celebratory tone. “But now in his absence the poems will have to stand alone,” she reflects. “And that is exactly what he would have liked.”

• Seamus Heaney: 100 Poems is published by Faber. To order a copy for £9.34 (RRP £10.99) go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99.

• Listen Now Again is at the Bank of Ireland Cultural and Heritage Centre, College Green, Dublin from 6 July.