That this show even happened is little short of a miracle. However, miracles are well within the grasp of a man whose influence on pop music is second to none.
By rights, after a well documented and astonishing 30-year battle against drug addiction, insanity, interminable family demons and creative castration, Brian Wilson should be dead. He should certainly not be in any fit state to lead us through a joyous three-hour show of unforgettable pop magnitude in his first UK appearance for almost 20 years.
And, the way Wilson walks almost ghost-like to and from the stage, his redundant keyboard which remains unplayed throughout and his bizarre physical mannerisms, all confirm this man has lived his life beyond extreme boundaries, visiting hellish vistas of the mind along the way, almost leading to his destruction.
But this is certainly no freak show, an opportunity to see just how peculiar Brian Wilson, idiot-savant, dumb angel, has become. Far, far from it in fact. The Royal Festival Hall is treated to an unprecedented airing of the epoch-defining 'Pet Sounds', Wilson's 1966 masterwork, from start to finish. Spliced on either side are some of the most heartbreaking and loving, inventive and life-changing songs ever committed to tape.
Throughout, Wilson sits centre stage, surrounded by a vast assemblage of musicians, who have nailed The Beach Boys sound with incredibly authentic style and no little panache and dynamism.
The ten players, eight of whom are likely to contribute backing vocals at any given time, encircle Wilson's still utterly resonant voice, to provide the harmonised and instrumental texture and density so favoured by Wilson and Phil Spector in their pursuit of The Wall of Sound.
The 40-song show, split into two sets, shifts seamlessly through the unparalled glory of the Wilson canon. 'Surfer Girl', 'She's Not The Little Girl', 'Please Let Me Wonder' and magnificent takes on 'Don't Worry Baby' and 'California Girls' represent the embryonic pop classicism that heralded the emergence of a mind-blowing talent.
Elsewhere, more rocking work-outs, such as 'Do It Again', 'Help Me Rhonda', 'I Get Around', 'Barbara Ann', 'Surfin' USA' and 'Sail On Sailor' give the show yet more of a charge, with Wilson, perhaps reading from his auto-cue, telling the audience to "kick-off your shoes."
Yet the highlight for many may well have been the distinctive complexity and sheer bravado of an astonishing collection of Wilson's finest, more obscure, recordings: the desolate 'Surf's Up' and 'Til I Die', the extraordinary, harmony carnival of 'Our Prayer' and a breathtaking plunge through the sprawling spaghetti western extravaganza that is 'Heroes And Villains'.
'Pet Sounds', is, of course, as manifestly breathtaking as one might expect from "The Greatest Album Ever", 'Good Vibrations' is unleashed like it was just another song, while, the sense of awe and delight at this experience, the genius of this man, is tangible throughout. Standing ovations are delivered time and again and continue to resound after Wilson allows a humble wave as he exits for the last time.
This was the day the true King of Pop reclaimed his crown. This was the day that Brian Wilson was, at long last, truly back.
