What links Dido, Grafton Street and the Progessive Democrats?

It's a stunning statistic: one in three Irish households has a copy of a Dido album. With No Angeland Life for Rent, Dido has amassed 22 million worldwide album sales, and in Ireland her figures make David Gray look like a Grafton Street busker.

It is de rigueur for music critics to sneer at Dido (and it's usually the sign of a bad one), a shibboleth that displays a fundamental ignorance of the power of melodic pop music. No, Dido isn't Iggy Pop and The Stooges or The Manic Street Preachers. Funnily enough, though, the Manic's Nicky Wire is thinks that Dido's White Flagis one of the best songs of the past 10 years.

Dido's new album, Safe Trip Homeis released today. It will doubtlessly sell a safe five to 10 million copies. On it you'll find a song called Grafton Street, which Brian Eno was brought in to produce. Dido insisted on hunting down the most sought-after producer in the world for this tune, which she feels is the most personal and historically significant song she has ever written and sung.

The story begins with Dido's dad, the Irish publisher William Armstrong, who was behind the publication of books by Bob Geldof and Boy George, among others. Armstrong's aunt was Hilda O'Malley, also known as "the most beautiful woman in Ireland" during the 1940s.

While studying medicine, O'Malley lived in a flat on Dublin's Raglan Road and was regularly admired (or "perved over" more like) by Patrick Kavanagh. O'Malley is the subject of the poet's famous Raglan Road, which was originally titled Dark Haired Miriam Ran Away. Kavanagh didn't want to use Hilda's real name in the poem, though he did at least note that Hilda, like a lot of women in Dublin at the time, ran away from him when he approached.

Famously, in Dublin's Bailey bar, Kavanagh showed his poem to Luke Kelly, who had the idea of setting it to an old Irish tune called The Dawning of the Day.

Hilda went on to marry Donogh O'Malley, a talented politician and minister in 1960s Ireland and a close associate of Charles Haughey and Brian Lenihan Snr. Donogh O'Malley died tragically early from a heart attack in 1968. His nephew is Des O'Malley, who went on to form the now defunct Progressive Democrats. This makes Dido a sort-of second-cousin-in-law of Dessie's daughter, Senator Fiona O'Malleys.

As a young girl, Dido was obsessed with great-aunt Hilda, the tales of her beauty and her role in Raglan Road. She know how important the song was to her father and, as a tribute to him and the song, she wrote Grafton Street.

William Armstrong died while his daughter was recording the new album. But Armstrong was thrilled by the success of Dido and her brother Rollo, who is in the band Faithless. One of the last things he said to Dido had to do with a newspaper report about Rollo.

"It says here that Rollo is cavorting on a beach in Ibiza with someone called Helena Christensen. Why is that in the newspaper?" Dido replied: "She's a well-known supermodel." He said: "So it's a good thing then?"

As her father lay dying, Dido would sing Raglan Roadto him and then she wrote Grafton Street- the title in itself a reference to its mention in Raglan Road: "Nothing's left that's safe here now, nothing will bring you home, Nothing can bring us the peace we had in Grafton Street."

• Safe Trip Homeis reviewed in this section. Hear Grafton Streeton www.didomusic.com/gb/home