A few days ago, at the Q awards, Foals' Yannis Philippakkis took the opportunity of ascending the stage to accept the Best Live Act award to take a not-too-subtle snarky swipe at Arctic Monkeys' Alex Turner, whose band was also nominated.

""It shows," quoth Yannis, the smell of vintage-shop mothballs and weed smoke no doubt haloing around him, "you don't need a backing track, you don't need affectation, you don't need Elvis Presley impersonations." The degree to which serious young Yannis was needled by the increasing weirdness of Turner's stage persona is telling.

It's that quiff. While it probably owes more to Arctic mucker Richard Hawley  and a Pulp-indebted idea of the Northern club crooner than the King, the inscrutable sense of humour evident in Arctic Monkeys' hair and attire of late does lead you to wonder: what do they mean by these leather trousers, those shades? Why is Turner combing his DA onstage at Glastonbury? Have they lost it? Are they high out of their minds?

The answer is, surely, that Arctic Monkeys are continuing to grow. Still only in their twenties, the former Authentic Northern Youths are playing with image and wit more than ever before, trying on some new guises. For those who feel like Yannis, as Turner puts it in the pit-inciting 'Teddy Picker', "Who'd want to be men of the people/When there's people like you?"

And what better venue to lark about in the dressing-up box of Proper Big Rock Showmanship (not for the first time, mind - megagigs are just what the Monkeys' do these days) than Earl's Court? It's a fantastic venue to watch a band who have serious stage presence going on; unlike most really big hangars, the floor space is far bigger than the tiered and seated; as a result, there's no need for big screens, the focus is all on the stage, which subsequently looms larger. And, if you're lucky enough to be upstairs, the view of the roiling sea of depravity below is as magnetic as the band. During older tracks like 'Flourescent Adolescent' and 'I Bet That You Look Good On The Dancefloor', there are circle pits over three-quarters of the way back. The balcony vertigo is delicious; I feel like I could plummet over the railing any time, to be torn to shreds by the Maenads or carried aloft on their hands like Daenerys Taergaryen at the end of last season of Game Of Thrones…

Anyway. Arctic Monkeys these days are more than up to managing such a mob. Turner points and flounces and purrs, Matt Helders hammers the drums while nailing note-perfect falsetto backing vocals. The light show is great, spots and mirrorballs on the floor trapping the band in a lattice of gold during the creepy-then-strident 'Crying Lightning'.

For me, the absence of some of the softer, subtler moments from Suck It And See such as the gorgeous 'Piledriver Waltz' and 'Black Treacle' are a shame. It was that album, with its unstrutty confidence and the grace of its slowly unfurling songs, the delicious, playful joy in words like "Letraset", "pamphlet", "post-mix lemonade" that finally made me a very late convert. This year's AM, while not quite as stunning, offers further revelations in the way their longstanding love of funk and hip-hop rhythms sees them transform wholesale into something slinky, sexy and far beyond Sheffield on 'R U Mine' and the deliciously finger-clicking 'Snap Out Of It'. Tonight, though, is far more about the crunch and heft and groove of those recent songs. When they sneak a snatch of 'War Pigs' into newie 'Arabella', it doesn't even feel that ridiculous.

While not all the tracks from AM can hold the attention (for me, 'Fireside' and 'Why'd You Only Call Me When You're High?') drag out their grooves too long), you can't argue with the perfection of their sleazy,  nightmare nightclub take on John Cooper Clarke's 'I Wanna Be Yours' and the divine creepy sexiness of Turner's plea, skinny leg perched cockily on monitor, of "Let me be your 'leccy meter…" Shiver Before they close with 'RU Mine?' he addresses the vast crowd like a shy teenage boy: "C'mere, I wanna ask you something…" The answer, though, is already pretty evident.