There was mass panic at the Roundhouse last night (May 31) as a cheeky cigarette sparked up in the Ladies loo, thus setting off fire alarms and forcing London patrons to be evacuated onto the mean streets of Chalk Farm for nearly two hours. But such a delay didn't stop the Chemical Brothers from playing a blinder set at the revered 160 year-old engine shed.

The Chemical Brothers, a.k.a. Ed Simons and Tom Rowlands, shuffled amiably onstage to the strains of new album opener "No Path to Follow," which was a dirge-y mix of medieval sounding folk and evil techno breakdowns. Upon the huge drum-kick of "Galvanize," a massive dot-matrix screen began to burn images into concertgoer's retinas and a massed throng of flouro'ed up hipsters, backpacked students and old school rave dads went proper grade-A mental for other Chemicals favorites such as "Hey Boy Hey Girl," and the full-on, tits-out, acid-gurning, rave-monsterized "Believe." The Klaxons-assisted newbie "All Rights Reversed," a gorgeous '80s-electro pop lullaby, let the sweat drip away and the lasers to settle as the Chemical Brothers once again confirmed: 'We are the Night.' RORY MACKIE / PHOTOS BY PAVLA KOPECNA

We asked: The Chemical Brothers are back and they've asked us to 'Do It Again.' So, if you had a chance to go back and do one thing again, what would it be?"

Name: Jemma Dawkins
Age: 24
Hometown: Brighton, UK
Occupation: Insurance
"I'd go back in time and do it all again."

Name: Matt Adams
Age: 28
Hometown: Brighton, UK
Occupation: Insurance
"The best holiday ever."

Name: Jeanie Overduin
Age: 22
Hometown: Amsterdam, Holland
Occupation: Model
"My whole life - I'd go to more gigs!"

Name: Emily Rushton
Age: 24
Hometown: Stoke, UK
Occupation: Events assistant
"Third year at school."

Name: Yanto Browning
Age: 27
Hometown: Brisbane, AUS
Occupation: Sound engineer
"I'd come to London six years earlier."

Name: Davide Savelli
Age: 20
Hometown: Faenza, Italy
Occupation: Chef
"Nothing, I regret nothing!"

Name: David Weller
Age: 19
Hometown: London, UK
Occupation: Student
"I'd go back to my art school interview, mess it up on purpose and concentrate on my music instead."

Name: Melissa Bennet
Age: 24
Hometown: Durban, South Africa
Occupation: Temp
"The last two years! And go to film school in America instead of becoming a temp."

The Roundhouse crowd / Photo by Pavla Kopecna

Hey Boy! Hey Girl! / Photo by Pavla Kopecna

Push the Button / Photo by Pavla Kopecna