How to detonate an atomic bomb in Dublin: first, take a generously-proportioned GAA stadium, fill it with 80,000 willing fans, download four dapper, middle-aged musical icons, plug in the amps and lighting rig, pull out the pin and stand well back.
This was the drill at 8.45pm last night when U2 blew up Croke Park - metaphorically, of course - and pulled a home victory out of the smoking rubble.
It's a fiendishly simple modus operandi that has worked for U2 for more than 20 years. Sure, they're often backed up by such heavy artillery as giant lemons and portable multiplexes, but essentially it's the four marksmen onstage who are responsible for that special U2 effect.
Sometimes they've only produced sparks, other times the whole thing has been a damp squib, but mostly - last night included - it has resulted in a supernova of sound and vision with a little magic thrown in.
U2's Vertigo tour has been on the road since March, and is already reaching dizzier financial heights than their last one, Elevation, which was the second most lucrative tour ever by a rock band.
But did it reach the rarefied heights of wonder and spectacle?
Can these old warhorses still cut it on the rock 'n' battlefield, or are they all clapped out and ready to be decommissioned?
As the foursome launch into Vertigo, Croke Park erupts in a breathless wave, and we expect oxygen masks to drop from above us. The weather is damp, the stadium looks grey, but the retina-searing flash of light onstage provides a welcome rush of colour. U2 are home again, and the lights are on.
They quickly follow with I Will Follow, side one track one from their album one Boy, and clinch the homecoming with an electrifying version of Electric Co. Bono punches the air triumphantly as Edge struts down one side of the curved pincer catwalk. Adam smirks in that endearing way, and Larry sits stonily underneath his canopy.
With the weather against them, U2 have their work cut out; after all, they have still to prove that they can still command not only our respect and attention, but also our undying devotion - not easy when they've become part of the furniture of modern Ireland, and some of us have reached the stage where we can take 'em or leave 'em.
But, on this first of three shows on their home turf, U2 are leaving nothing to chance. A rousing Elevation gets the crowd whooping, and New Year's Day brings us back to a red-letter day when U2 made an early entry into the world's rock 'n' roll yearbook.
Beautiful Day doesn't quite sweep the clouds away, but I Still Haven't Found What I'm Looking For finds just the right note - this is the moment U2 finally connects with their constituency, and when the giant megapixel backdrop fires up for City of Blinding Lights, and Bono announces, "oh, you are so beautiful tonight", we have become believers again.
Love and Peace may not match Desire for simple three-chord slickness, but Sunday Bloody Sunday and Bullet the Blue Sky get down to the real business of what U2 are about: big, blood-red anthems that were built to last - and do.
"How long must we sing this song?" asks Bono. As long as you can still hum it, mate, we'll keep singing it.
