Croker crescendo for One Direction boys

They’re the world’s biggest boy band and maybe the world’s biggest band full stop.

How extraordinary that just four years ago the soon-to-be members of One Direction were anonymous strivers hoping to break into show business via Punch and Judy talent show The X Factor.

Not since The Beatles, surely, have a bunch of polite young men with interesting hair rocketed from obscurity to mega-fame so quickly and, it has often seemed, effortlessly.

On the opening date of their European tour, the scale of their appeal was something to behold.

One Direction packed Croke Park for the first of three concerts last night and, when they materialised at the top of a ramp, accompanied by volleys of fireworks, the screams were past deafening (the crowd was overwhelmingly, though not exclusively, young teenage girls).

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Rebecca Ryan, Kelly Farrell and Molly Sheridan

As the dozens of hand-written signs held aloft attested, each of the quintet has a substantial fan-base — not surprisingly, the loudest yells were for Niall Horan, the Mullingar native with the impish grin and vertical quiff (someone had done brisk business in ‘We Heart Niall’ flags) .

Dwarfed by a vast multi-tiered stage, they kicked-off with recent single ‘Midnight Memories’, a boisterous guitar number which suggests their days as purveyors of slick pop may be at an end.

While boy bands are generally advised to approach full-throttle rock music with caution, One Direction threw themselves into the song (enhancing their cred, Horan chugged a guitar).

Such is their lad-next-door charisma they could probably make twerking acceptable.

Jumping for joy were Annie May Doaka and Sophie Vickerstaff on their way to the concert.

Outside of Ireland, curly-mopped Harry Styles is regarded as the de facto leader. He certainly emanated frontman charm at Croke Park, notwithstanding an indecipherable ‘conas atá tú’ (blustery conditions made it seem as if his hair had a life of its own).

Then, it’s not as if the rest of the troupe are exactly anonymous: they can all sing, are accomplished movers and seemed visibly comfortable with 80,000 people chanting their names.

The concerts are the beginning of a busy weekend for the five-piece.

Today they fly to Scotland for a lunch-hour gig, before returning to Dublin for the second of three dates that will see them perform to a cumulative audience of 240,000.

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Fans from Belfast:, from left, Taylor Beattie, Emily Plunkett and Jayla

Nellins.

Whatever the future holds — the gossip press was full of break-up rumours at the start of the year —they will surely look back the Croke Park gigs as a highlight of their rollercoaster career.

“Croke Park 2014,” said Horan, struggling to unwrap a tricolour in the teeth of a gale. “We were here and so were you.”