All Saints are back. For a certain kind of 30-something – the kind who never quite identified with any one of the Spice Girls; the kind who likes a song with a breathy spoken bit; the kind who might, for example, have spent her GCSE years ironing her hair, wearing combat trousers and fake black-rimmed glasses, forever on the hunt for the perfect vest top – this is pretty major news.Last week, trusty followers of the @AllSaintsOffic Twitter account – What? – released a series of black-and-white pictures of the quartet in the studio looking for all the world like the Noughties had never happened. There was Melanie goofing about with her massive smile; there was Shaznay looking moody – oh Shaznay, never change – and there was Natalie, or was it Nicole, pouting into a microphone in leisurewear.Today [Wednesday] the band confirmed their official return with a new single “One Strike” out next month, a candid interview with i-D and a new album, Red Flag, due in April. It’s not their first reunion. For a band whose close harmonies sold 11 million albums and got them five number ones, they've had their rifts. The band first split up in 2001, then reformed in 2006 – “for the money”, according to Melanie – releasing the flop album Studio 1 before splitting up properly in 2009 when Melanie (again) said they would “never, ever get back together” . And then, in 2014, they went on tour with the Backstreet Boys. It was doing those nostalgia gigs that made them realise they wanted to reunite for real.So here they are, in their forties, on their third reunion and that’s a very good thing. Here are eight reasons why.