Cast your mind back to 2003.

Tony Blair was still the Prime Minister, the London congestion charge was introduced, the Iraq war began, ‘Dirty’ Den Watts returned to EastEnders after a 14-year absence, Jude Bellingham was born and Concorde made its final commercial flight.

During the same 12-month period, four young men including one from Bromley Cross – Tom Fletcher, Bolton's Danny Jones, Harry Judd and Dougie Poynter – got together to form McFly, a pop-rock act that within a year had taken the UK charts by storm.

Since then, they have had 18 consecutive top 20 UK chart singles, seven of which have reached No 1; they’ve also sold more than 10 million records worldwide.

In 2013, the quartet teamed up with their old mates from Busted to form supergroup McBusted, and they’re planning on doing something similar again next year – tickets are already available and have been selling like hotcakes.

Twenty-one arena dates have been announced, with 110,000 fans expected to see them in London alone.

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But before that, McFly (they named themselves after Michael J Fox’s character in the Back to the Future franchise, in case you were wondering) are celebrating their 21st anniversary: “We still can’t believe it’s been 21 years!” The band’s members claimed in a statement released by ITV ahead of this weekend’s TV special.

“But what a way to look back on many fond memories and celebrate with the people that made it all happen – our fans. We had the best time playing the shows and can’t wait for audiences at home to get the chance to party with us – we’ll only turn 21 once!”

If you haven’t guessed already, the programme was recorded at The O2 in London during a series of celebratory concerts, and features performances of some of their greatest hits, from their breakthrough single, Five Colours in Her Hair, to tracks from their most recent album, last year’s Power to Play.

We’re also promised action from backstage, as well as a glimpse into how the shows were put together.

Liz Clare from production company Gold Dust Films comments: “Gold Dust Films has loved being part of this massive celebration of McFly and 21 years of their music. It’s been a passion project for the band and we are delighted to be bringing this very special concert and all their backstage fun to ITV. But most importantly we are pleased to be able to give their fans the chance to be part of the biggest party in town. Get ready to be McFly’d!”

“Bringing the band’s 21st celebrations to audiences at ITV1 and ITVX is really exciting and we can’t wait for fans to see the show – it’s fantastic,” adds Katie Rawcliffe, Head of Entertainment & Daytime Commissioning at ITV. “We’d love to celebrate the next milestone birthday together too!”

No doubt the band’s thousands of fans would love that too – here’s to the next 21 years, boys!

McFly the 21st Birthday Party will show on ITV1 at 5.30pm