Ladytron's 2001 debut, 604, is one of the forgotten gems of the early noughties. At a time when garage rock was making its breakthrough, their Kraftwerk-inspired sparseness stood out from the rest.

A rough diamond, its hollowness was its charm, and the whispered, robotic vocals, shared by Helen Marnie and Mira Aroyo, gave it an eerie edge, unexplored in modern electro.

"When we first started out, there weren't that many indie bands using synths to write songs," says Aroyo. "Whereas now almost every band has a synth. I think pop music is a lot more diverse than when we first started."

Which might explain the sudden departure from their tried and tested formula.

Their second album Light and Magic spawned minor hits Seventeen and Evil, but it was 2005's Witching Hour that signaled their transition into the mainstream.

"It wasn't conscious. We are not the kind of people who are satisfied by finding a formula and repeating ourselves, so every album we have tried to write new and better material than the one before. Also we have learned a bit along the way and played live a lot, which we hadn't really done until after Light and Magic was released.

"That was probably the main influence on our sound and as a result Witching Hour and [new album] Velocifero sound tougher and fuller than the previous albums."

Bulgarian Aroyo teamed up with Liverpool-based DJs Reuben Wu and Daniel Hunt in summer 1999.

Shortly after, Glaswegian Helen Marnie was recruited, they stole the title of a Roxy Music track as their new band's name, and got to work on 604.

Their fourth album, Velocifero, was released earlier this year, and Aroyo seems to have found her USP within the vocal duo. Two tracks - Black Cat and Kletva - are sung in her native tongue, to devastating effect.

Emotionless, blank vocals recited over thundering drums and blistering, gothic synths make the former one of the best album openers for years.

But Aroyo refuses to become complacent. "We'd like to get recording a new album as soon as possible. We just need to get a break from touring.

"We've been touring pretty much none stop. We were in the USA and Canada for a couple of months, then we did festivals in the summer, then we went to Australia and played there. Now we're in Europe..."

London is the next stop on their worldwide tour, so what can we expect from the show?

"Pyrotechnics and dry ice! Helen and I are going to be shot out of a cannon ball. Lions will be jumping through fire hoops..." she jokes. "I wish! In reality? A nice, light show and some more songs from Velocifero that we haven't played before. And some very old songs too..."

Ladytron play Shepherd's Bush Empire on November 21. For more information call 020 8743 5384