Sir Peter Blake's 28-year Under Milk Wood labour of love

It has taken 28 years to complete but renowned artist Sir Peter Blake's secret passion, a piece of work based on his obsession with Dylan Thomas's play for voices Under Milk Wood, has finally been revealed.

His illustrations using pencil, watercolour and collage - which detail every aspect of Thomas's fictional seaside village Llareggub - are going on show at National Museum Cardiff.

It is a new body of work for Blake, who is often described as the godfather of Pop art, and one which he maintains is every bit as important as the others.

And it is lucky he says that he has finished it in time to launch the Dylan Thomas 100 Festival, a celebration to mark 100 years since Wales' best-known poet's birth in Swansea.

"It could have gone on for ever," admitted Blake. "But the festival was as good a place as any to stop. I am thrilled that it ties in with Dylan Thomas 100. It's perfect really."

But it could have all been so different. Llareggub could have taken just a year of Blake's life, albeit in a different format.

Blake said the original plan back in 1985 had been to create a series of wood engravings to illustrate Under Milk Wood in a limited edition book.

Ironically, Blake decided that was taking too long and abandoned it.

But a lifetime obsession had begun which meant Blake listening to the play or reading it at least twice a week.

Blake first became aware of Thomas half a century ago when the artist was a student at the Royal College of Art, and fellow Welsh students there picked up on the play immediately.

Sir Peter's Blake's Llaregubb uses techniques of collage to illustrate Under Milk Wood

The artist borrows from images to depict some of the play's lengthy cast - here Captain Cat is based on the racing driver Tommy Sopwith, as well as the artist's own beard

He also annotates his watercolours of scenes from the well-loved radio play

"I never met him no, but I started at the Royal College in October in October 1953 and he would have been in Soho. We may well have been in the same pubs," he said.

Thomas died in New York in November 1953.

The poet was, in fact, one of the crowd - at John Lennon's suggestion - on Blake's famous design for the cover of The Beatles' Sgt. Pepper's Lonely Hearts Club Band from 1967.

But their paths never crossed and Blake reckons that if they had met back in the 50s, Thomas would not have had the time of day for him.

Blake beavered away on visualising Llareggub for all these years largely at home in the evening when his day job was over.

"It was like there were two mes," he explained. "Peter Blake the painter and Peter Blake the illustrator. They're both as important to me as each other. This is not a hobby."

There are 170 illustrations in the Cardiff exhibition - some collage, others watercolours - and 60 pages of pencil portraits of the characters who fill Thomas's famous play.

Included in the exhibition, there is even Blake's train ticket from a 1986 exploratory visit to Laugharne in Carmarthenshire (where Thomas penned Under Milk Wood) when he chanced upon Thomas's wife Caitlin visiting for the first time in 30 years.

Working on the project has been a big part of Sir Peter Blake's life

If you look closely you may recognise some familiar faces within those drawings of Nogood Boyo, Captain Cat and Rosie Probert and the rest of the play's rich cast list.

All the portraits are both imaginary and real because Blake believes that a face cannot be invented so he borrows from images he finds.

Among the faces he has borrowed are Richard Burton and Elizabeth Taylor, racing driver Tommy Sopwith, actress Billie Piper, and even broadcaster Sir Terry Wogan whose familiar features have been used in a portrait of a woman.

Eventually, Blake said he would like the exhibition to find a permanent home in Wales.

For now it will run from 23 November to 16 March in Cardiff before moving onto Oriel y Parc in St David's, Pembrokeshire, next May. Trips abroad could follow in the wake of the Dylan Thomas centenary celebrations which Blake expects to play a full role in.

"If we met now, I think we would have something to talk about, a common interest in Under Milk Wood," said Blake.

"But," he added with a laugh, "If we did meet now, he would be out of here in the bars, getting drunk."

A BBC Wales programme Under Milk Wood in Pictures showing Sir Peter Blake at work on Llareggub will be screened on BBC One Wales on Monday, 25 November at 23:35 GMT