Gwyneth Paltrow duets with Jay-Z

Paltrow attended an aftershow party following her performance

Actress Gwyneth Paltrow has made a surprise appearance with rap legend Jay-Z at London's Royal Albert Hall.

The star of Shakespeare in Love and Proof sang the chorus of Song Cry from the rapper's classic Blueprint album.

"She was a bit nervous but her performance was really excellent," says 1Xtra DJ G Money, who was at the gig.

Other onstage guests included Paltrow's husband, Chris Martin, Beyonce and rap star Nas. It was the first hip-hop gig to take place in the Royal Albert Hall.

"It was an historic event," said G Money. "We were in the same seats that you've seen at the Proms. It was amazing."

Jay-Z, whose real name is Shawn Carter, was backed by a 25-piece orchestra and a DJ for his set.

Surprise performance

Chris Martin duetted on an untitled song from the rapper's new album, and added vocals to another track from Blueprint, called Heart Of The City (Ain't No Love).

The Coldplay star's performance had been rumoured before the concert, but his wife's appearance was more of a surprise.

"People were like: 'Who is this chick that's in the spotlight?'" said G Money.

Jay-Z is one of the most successful rap artists of the last decade

"Then Jay-Z said: 'I want people to wish a happy birthday to my good friend Gwyneth Paltrow'.

"Everyone was like: 'Are you for real?'"

Jay-Z's hits include Hard Knock Life, Dirt Off Your Shoulder and Girls, Girls, Girls. The rapper announced he would retire in 2003 after releasing The Black Album.

The following year, he was made president of influential hip-hop label Def Jam - home to artists such as Kanye West, The Roots and Ludacris.

He has made guest appearances on several records in recent years, including Beyonce's recent number one, Deja Vu.

Jay-Z is widely believed to be dating the R&B star, although the couple have never discussed their relationship in public.

The rapper is due to come out of retirement with a new album, Kingdom Come, in November.