They thought of asking Paul McCartney, a royal, a politician or a poet – but, in the end, the £72m museum celebrating Liverpool's eclectic heritage will be opened on Tuesday by Finn O'Hare, a six-year-old-boy, who wrote to "Mr. or Mrs. In Charge of the Museum", explaining that he was "good at opening things".
The extraordinary new arrival on the city's river Mersey waterfront – "like a giant stone Twix bar", according to one woman who peered through the fence at the weekend – is described as "the largest newly built national museum in Britain for more than a century".
Inside, at the top of the giant spiral staircase, visitors will find an exhibition as quirky as its home: unseen photos by Mike McCartney celebrating his native city – and inevitably, his slightly more famous brother Paul. Sir Paul, or "our kid", as Mike calls him, is seen starting to buckle with tiredness, finally heading off the stage with one last weary wave to the roaring crowd after an epic performance at the Anfield stadium in 2008, the year his city held the title of European Capital of Culture. His brother says it was "a rip-stonking performance" in front of an audience of 35,000 – "half of whom were our family".
As well as photographing wheelie bins, rainbows and his own shiny Beatle boots, Mike McCartney also captured Bono backstage, mugging up on his lines by the light of a little torch before going on stage at the Echo Arena to present Paul with the MTV Ultimate Legend award. "Bono said: 'There is one person in the hall tonight whose work is immortal,'" Mike recalled, adding - as proud performer of Lily the Pink, the Christmas 1968 chart-topper which held the number one slot for four weeks – "I didn't know he was a Scaffold fan."
"It's a high honour when the National Portrait Gallery, the Rock'n' and Roll Hall of Fame and the Smithsonian Institution in Washington DC ask for your photographs. But it's the icing on the cake when your hometown asks for an exhibition to open their brand new Museum of Liverpool," he writes in his introduction to the show.
"I hope these images give some insight into the unique people this area produces, and that their impossible-to-suppress, self-deprecating humour shines out of the photographs."
That spirit is laced through the museum, which includes bitterly funny comments, filmed interviews and objects donated by Liverpudlians – including Mr J Mackin's 1992 Anfield Travel Club card. There are quotes from the late community activist Margaret Simey – who, as chair of the Merseyside police authority, questioned their actions in the Toxteth riots – "The magic of Liverpool is that it isn't England" – and Beatle George Harrison – "Good place to wash your hair, Liverpool, nice soft water."
The exhibits include comedian Ken Dodd's tickling stick, a pair of gold lamé knickers worn on stage by poet and artist Adrian George, the Brookside Close street sign from the TV soap, the skeleton of Ambush II, the 1900 Grand National winner, and the school-hall stage on which John Lennon and Paul McCartney first played.
Despite the swaggering statistics – the building is longer than the Anfield or Goodison Park pitches and has a navigable canal and a railway tunnel running underneath – the project has had to overcome a few teething problems. Conceived as a replacement for the Museum of Liverpool Life to open in 2008, it became enmeshed in design rows over developments on the historic Pier Head, the setting of the Three Graces buildings, which threatened to cost the site its Unesco World Heritage status.
National Museums Liverpool fell out with both the architects, the original Danish 3XN and the Manchester-based AEW. And, earlier this year, it had to pay £750,000 compensation to the Port of Liverpool building for partly blocking its view of the river.
However, now that it is opening, with more galleries due later this year, the museum authorities are convinced the building, with its spectacular views from huge windows, will become as well-loved as its neighbours. Janet Dugdale, the museum's director, said: "Liverpool is a very demanding city and that is a great thing when you're creating a city museum."
