Katy makes it two in a row
Katy Perry celebrated her second week at the top of the charts with her hit California Gurls.
The song, which features rapper Snoop Dogg, is the first single from her forthcoming album Teenage Dream.
It is her second UK No 1 after the 2008 hit I Kissed A Girl.
For Snoop Dogg, it marks a first UK No 1 single after more than 20 Top 40 hits over a 17-year career.
There was also a second week at the top of the album charts for US rapper Eminem whose album Recovery went straight in at No 1 last week.
Since releasing his major-label debut The Slim Shady LP in 1999, Eminem has sold more than 78 million albums worldwide, including more than 7.5 million in the UK.
Second spot in the singles chart went to B.o.B's Airplanes featuring Hayley Williams which climbed from last week's number 12.
There was a new entry for Enrique Iglesias's I Like It featuring Pitbull which went straight in at No 4.
In the albums chart there was a new entry for Scissor Sisters. Their third album Nightwork was the highest new entry at No 2.
Alicia Keys completed the top three - her album The Element Of Freedom climbing three places from No 6.