How typical of the renegade Aussie to crash the pommy party like he were the guest of honour. He even hijacked the encores, "dishing up" (his phrase) renditions of "The Londonderry Air" and "Mock Morris" (the latter in its most "elastic", meaning elaborate, scoring) while our ears were still humming from the resounding self-portrait of Edward Elgar that is the finale to the Enigma Variations. But then, Percy Grainger was never one to stand on ceremony. And besides, he was in truth a self-appointed pom, coming up and over from down under with tunes like "Country Gardens". Authentic English folk tunes -but by Grainger.

Saturday was his night. And for one good reason. None of the recent recordings of his "imaginary ballet" The Warriors could possibly have prepared us for its impact in the hall - this hall. Overblown, overscored and over here it may be, but there is nothing, really nothing, quite like it outside the imagination of Western music. So who and what are these warriors? Human kind at its basest? Our tribal instincts run amok? Is it just, to quote Grainger himself, "a united show of gay and innocent pride and animal spirits fierce and exultant"? Or is there a deeper resonance, a pacifist message, in the long, lonely, heckelphone solo that is the work's heart and soul? Such questions are best left unanswered, because the joy of Grainger is in the conflict and contradiction, the incongruity, the sheer bloody-mindedness of the inspiration. Jaunty Victoriana piles head-on here into rampant gamelans (eight players ranged over the gamut of "tuneful percussion") while three grand pianos keep their collective fingers on the pulse, beerily driving us forward all the way from the Old Kent Road to Polynesia and the Outback. At one point, the whole brassy conflation moves off-stage while lamenting strings try not to listen. But the dance goes on - the apotheosis of the dance (isn't this where Beethoven's Seventh left off?) - and the end, when it comes (replete with rowdy Albert Hall organ), is enough to make your eyes water. Richard Hickox and the intrepid BBC Philharmonic (and friends) gave it a rousing Proms welcome. Where else?

So, in an evening when even Britten's Young Person's Guide to the Orchestra sounded like the warm-up (and notwithstanding eloquent exhibitions from the oboe and cello department, this was not a performance that ever quite peaked), one could only sympathise with Jonathan Harvey, whose Percussion Concerto was receiving its world premiere. And yet it exhibited an odd kind of kinship with the Grainger. An altogether different set of rituals, but rituals none the less. Its charismatic dedicatee, Evelyn Glennie (looking exotic in gold-threaded mandarin coat and open-sided PVC leggings), moved gracefully, silently to the Mark Tree (a rack of tiny bells sounding like the sprinkling of fairy-dust) to set the first of them in motion. This is a "marimba-centric" kind of piece (says Harvey), and Glennie - as you can see and hear through the blur of flying mallets - is the Paganini of the instrument. Initially, her athletic game of tag with the orchestra proved absorbing. But only initially. Harvey's first movement is too long and too limited, too unvaried, in expression. It favours the hard-edged, woody attack of the instrument at the expense of its softer tones. It is fitful, explosive, "broken-biscuit" music, twitchy configurations of notes going nowhere. The slow movement doesn't come a moment too soon. When it does, you welcome the space, the prevalence of vibraphone and Balinese gamelan (which looks splendid but is again somewhat short-changed in the equation). There's a transitory, ephemeral quality to this music which sounds more like the music Harvey wants to write. At the end of the piece, Glennie brushes the Mark Tree (the tree of life?) once more, and a piccolo and then cellos imitate the effect. It's rather sweet. The beginning of an interesting idea. But then it's over.

And then it's Elgar. And any performance of the Enigma Variations that makes the transition into "Nimrod" so magical (that sustained G in the first violins little more than a vibration in the air) has my ear for the duration. Hickox and his players sketched vivid likenesses of Elgar's "friends pictured within". As for that mysterious, unattributed Romanza with its hazy clarinet recollections of Mendelssohn's Calm Sea and Prosperous Voyage (beautiful playing), that was strange - no, weird - enough to be Grainger.

Concert repeated on BBC Radio 3, 2pm today Edward Seckerson