gallery: Katy Perry in pictures
Katy Perry at the Grammys in 2012
Kanye's all tensed up after his show (look at the fist!) as he poses with Katy Perry at his Paris Fashion Week after show party
British hair stylist Vidal Sassooon - born in Hammersmith, London in 1928 - revolutionised style with his popularisation of the bob.
Sassoon took the classic cut, which first emerged at the turn of the century, and made it shorter and cleaner, freeing generations of women from regular trips to the salon.
In tribute to hair's ultimate rock star, we take a look at some memorable pop music bobs from years gone by.
Katy Perry gets the blues
Katy Perry
Katy Perry shows off her new orange locks while promoting her perfume in Toronto.
Katy Perry performs in 2010.
Katy Perry plays T4 on the Beach
Katy Perry attends GRAMMY Nominations Concert Live!! on December 1, 2010 in Los Angeles, California.
Katy Perry models in metallics
Katy Perry in one of elaborate costumes
Justin Bieber with Katy Perry in 2010
Katy Perry looks her usual stunning self in this press shot for her Teenage Dream album.
Katy Perry gets the blues
17. KATY PERRY
Next up in our Pop Powerlist it’s colourful Californian Katy Perry who, with awards fighting for space on her mantelpiece, record sales through the roof, endorsements galore and media buzz surrounding her recent divorce from funny-man Russell Brand at an all-time high, finds herself at number 17 on our list.