Pop superstar Beyonce has stepped up her security over fears about an obsessive fan, according to a U.K. report.
Editors at The Sun claim staff at London's Twickenham Stadium have been told to be on the lookout for Bassey Essien at the Crazy In Love hitmaker's gig at the venue on Saturday (01Jun13).
Beyonce won an anti-harassment order against Essien, who began sending threatening letters to the star in 2009, at Britain's High Court in 2011, prohibiting him from pestering her.
The newspaper reports that the singer has been sent threatening notes ahead of The Sound Of Change concert, and an insider adds, "Staff have been briefed on the situation and pictures of him have been passed round. They've been told to keep their eyes open and be extra vigilant.
"Security has been increased on a few engagements now, especially for her U.K. promo. It is believed similar letters to the ones that Essien sent have been received."
Jennifer Lopez, John Legend and Timbaland are also among the stars set to perform at the charity concert, which aims to raise awareness of women's issues around the globe.