Parties: Grayson Perry zigs and Bill Nighy zags at Tate Britain's summer party

Guests ummed and ahhed as they wound themselves around Eva Rothschild's giant, room-encompassing zig-zag of a sculpture that was the centrepiece for Tate Britain's summer party on Monday.

The checklist for an art-crowd evening such as this is scant: luminous, clashing colours are a must; an obscene knowledge of art (or at least a bluffer's guide) is essential; and flat shoes that aid agility while hopping from one exhibit to the next are useful. But tonight was all about broken legs, too. Alison Goldfrapp was seen hobbling around in a cast, while the eccentric artist (and aristo) Lord Bath was wheeled around by his girlfriend, Trudie. (But ooh la la la la, Goldfrapp hotfooted it out of the party early with a friend...)

Step up instead Grayson Perry, who, after turning down an invitation from two young ladies for a "girly night out" ("God no, I'm not camp enough and besides, my wife would kill me") singled out suave actor Bill Nighy for particular abuse. "Oh, I'm in trouble with my wife, I'm so louche – that's all his shtick is, isn't it?" Perry quipped in front of an adoring group.

Leaving personal sniping to one side, what did Nighy make of this evening's works? "I realise it's a cliché, but I don't know enough about art to buy any," confessed the prolific party-goer, begging the question of what was it about tonight's bash that had appealed to him. But while Nighy might not be up on his sculpture, he does know a thing or two about the upcoming Harry Potter movie, confiding that he'll be appearing in it as Minister for Magic, Rufus Scrimgeour.