Waterson Family & The Eliza Carthy Band, Royal Festival Hall, London

The family that plays together...

Eliza Carthy led her deft ensemble through a mariachi-flavoured ode about a lecherous sleazebag who gets his comeuppance thanks to a pair of French hitchhikers. A strange way perhaps to celebrate the 70th anniversary of the UK's, if not the world's, longest-running independent label and one that for a long time acted as a refuge for traditional British music. If you look carefully at the label's history, though, strange resonances do crop up.

As Topic's mammoth birthday compilation, Three Score & Ten, reveals, The Oldham Tinkers mined similar Latino bawdiness during the label's peak period with "The Lancashire Toreador". Worth remembering, for with its beginnings in hard- left politics, Topic has often been tarred with a certain ideological correctness, especially recently, as the likes of guitarist Bert Jansch and the delicate Vashti Bunyan, who would not have been touched with a barge pole back in the Sixties, have enjoyed newfound fame.

Yet as The Watersons' matriarch, Norma, attests, Topic took her group on "when no one else was interested". Formed in the late Sixties, this familial quartet set a gold standard for unaccompanied vocals, a theme carried on in the next decade with husband Martin Carthy. Later came Waterson: Carthy, with the couple's daughter Eliza. Here, the Waterson Family took the stage as a more diffuse concern – nine people, related by blood or marriage, lined up together.

Eliza confidently marched to her mic stand, while uncle Mike slouched on with a pint in his hand and a flat cap on his head, as if leaving the pub for a sneaky fag. It is quite a coup, or as Norma dryly comments, "It's weird trying to round them all up". Their collective sound was impressively supple as they moved from the wide-eyed asceticism of the ancient hymn "The Good Old Way", through the sashaying, updated shanty "Some Old Salty" to Mike's own anthemic "Rubber Band". The men laid an unadorned framework, sturdy as oak, for the female singers to soar over the top with intuitive ease.

Such an extended grouping overwhelms individual personalities, so the most memorable moments came elsewhere. Martin and Mike separately leavened proceedings with light humour, while Eliza was joined by her uncle's daughters, Rachel Straw and Eleanor Waterson, for an elegant, mournful "General Wolfe". If anyone deserves to be mourned it is Norma's sister and Watersons founder, Lal, who emerged as a distinctive songwriter during the Seventies, yet passed away suddenly in 1998. Her daughter Maria Gilhooley provided an exemplary reading of the otherworldly "Fine Horseman", though she was too introverted to convince on her own "Mind the Gap".

Midway through the set, Eliza herself takes over to show how she has matured into one of our most compelling contemporary songwriters. Given the celebratory occasion, "Little Big Man" seems particularly apt, as she praises the assets of "chubby women" – "you could have been rocking on a big sea," she admonishes the song's subject. That and "Mr Magnifico" come from Eliza's current Topic album, Dreams of Breathing Underwater, where she has moved on from her roots background to occupy a distinctive hinterland that takes in jazz, rock and chanson.

A backing band with accordion, cello and double bass are well placed to show that Topic is in no way hidebound to taste concerns, if ever it really was. With so many generational permutations, the one real loss tonight is Norma's soulful voice, one that gets drowned out, despite the fact that she is enjoying her own late-flowering solo career. Bar the curt verses to the traditional sea shanty "Shallow Brown", she gets no chance to shine herself. At least Norma knows that the Waterson legacy is in safe hands.