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Lily Allen

Dave Hogan/Getty Images

Get down, Lily Allen, get down.

While grooving during her set at The Other Ball at One Mayfair in London tonight, the "Hard Out Here" singer flashed what at first appeared to be her fanny.

But upon closer inspection (it's a dirty job, but someone's got to do it), Allen was wearing a pair of dark underwear that just left a fair amount of upper thigh-and-beyond area exposed.

All in all, her most private parts remained covered, though the slit in her long dress kept her legs exposed throughout.

Lily Allen

Dave Hogan/Getty Images

The recently redhaired songbird's outfit was actually more conservative than some of her recent ensembles, including the sheer, pasties-exposing top she wore for a benefit at London's Royal Albert Hall in April or the Spanx-only look she danced around in in a home video posted to Instagram.

The Other Ball, meanwhile, benefits Arms Around the Child, which serves to protect at-risk and exploited youth. Mark Ronson hosted the event and those who made the ultimate 20,000-pound ($34,486) contribution were treated to at least 10 front-row seats, a meet-and-greet with the celebs in attendance, a gift bag and other VIP perks.

Including the knowledge that Lily Allen didn't forget her underpants at home.