There’s something fitting about Pentangle’s maiden show in 1967 having been at the Royal Festival Hall. That the South Bank’s state-of-the-art auditorium – built in the spirit of postwar optimism and synonymous with the promise of tomorrow – should have launched Britain’s first and, indeed, only jazz-folk supergroup seemed fitting.

Bert Jansch, John Renbourn, Danny Thompson, Terry Cox and Jacqui McShee may have served apprenticeships in established musical idioms, but together, the sound they made was uniquely hard to pin down. Two soft beats on the floor-tom from Cox signalled the beginning of Light Flight and, indeed, Pentangle’s return to the Royal Festival Hall after a 36-year absence.

For those of us who count this paean to swinging London among their earliest memories it was as though all our Proustian chickens had come home to roost. Not for the last time, McShee – dressed in the sort of loose-fitting floral trouser suit favoured by women who were groovy in the 1960s – introduced a song with reference to the fate that befell its female protagonist.

In this case, it was House Carpenter that Pentangle readied themselves to play. As John Renbourn lowered himself on to the floor and locked into a hypnotic sitar melody, Jansch used a banjo to rattle all the dormant ghosts from this Appalachian tragedy.

McShee, as ever, was all cut-glass English precision. When the time came to play A Maid That’s Deep in Love, she pointed out that, “the woman doesn’t get it in this one, but only because she dresses up as a man”.

If folk songs were played with a jazz zip, then jazz tunes were subtly transformed by the twin talents of two guitarists who had long since broken down blues, folk and a love of medieval music into one rich source of fuel.

A case in point was I’ve Got a Feeling – a Miles Davis tune with words added by Jansch.

As McShee serenely imparted the words, Danny Thompson quietly set about reminding everyone why his number is the first on the list of any musician looking for someone to play upright bass on their records. Here and on the group’s signature wig-out Pentangling, Renbourn’s impromptu cheers spoke for everyone in the room as Thompson cut loose with a hair-raisingly expressive solo.

While other returning groups from recent years – Kraftwerk and My Bloody Valentine spring to mind – struggle to distinguish themselves from all the artists they went on to influence, Pentangle have no such problems.

Forty years ago there wasn’t a band on the planet that sounded like them. In 2008 there still isn’t a band on the planet that sounds like them. It’s an absolute joy to have them back.

— July 1: Cardiff, St David’s Hall. Box office: 029 2087 8444. Tour details at www.myspace.com/pentangle

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