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The man at the heart of a lawsuit brought by 9/11 families had extensive links to Saudi government officials and went paintballing with one of al-Qaeda's future leaders, video obtained by the BBC reveals.

The new evidence undermines Omar al-Bayoumi's 25 years of denials that he was an extremist and a Saudi spy.

The videos form part of the lawsuit against Saudi Arabia, which argues the country was complicit and that Bayoumi aided two of the hijackers.

Bayoumi and the Saudi government did not respond to the BBC's requests for comment. The FBI declined to comment.

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