UPERSTAR Beyoncé is stepping up security at her Twickenham stadium gig — amid fears of a British stalker.

Staff have been told to watch out for obsessed fan Bassey Essien when the Crazy In Love singer headlines the Sound Of Change concert on Saturday.

It is believed she has been sent sick threatening letters.

Essien has already been warned to stay away from Beyoncé, 31 — who won an anti-harassment order in the High Court in 2011, prohibiting him from pestering her. Court papers revealed Essien, of South West London, had been sending threatening letters to the star since 2009 and made a bizarre claim she was an imposter who had killed the real Beyoncé.

A source said last night: “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.”

The source also revealed: “Security has been increased on a few engagements now, especially for her UK promo.

“It is believed similar letters to the ones that Essien sent have been received.”

Beyoncé is due to play a 45-minute set at London’s Twickenham.

Other acts at the concert, organised to promote education, health and justice for women, include Florence and the Machine Jennifer Lopez and Rita Ora. Meanwhile 16-times Grammy award winner Beyoncé put one fan firmly in his place after he slapped her on the bottom while performing on stage on Monday.

The star, in Denmark as part of her Mrs Carter world tour, had just handed her microphone to fans so they could sing along with her track Irreplaceable, and was turning to go back to the main stage, when the cheeky fan struck. Beyoncé, who is married to rapper Jay-Z, 41, looked directly at him and snapped: “I will have you escorted out right now, alright?” Last night her spokesperson refused to comment.

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