Slain Osama bin Laden's right-hand man spent time designing a vacuum cleaner and reading Harry Potter novels in a Romanian jail.
A former senior agency officer said the CIA let Khalid Sheikh Mohammed, 49, who is a qualified engineer, design the vacuum cleaner to stop him going 'nuts' in a Romanian basement cell 10 years ago.
The key surviving 9/11 plotter, now in Guantanamo Bay, was allowed Internet access to help with his vacuum blueprints, the Sun reports.
Mohammed, the admitted mastermind of the 9/11 terrorist attacks, has asked his jailers whether he could embark on an unusual project.
He is understood to have worked on the plans after being moved to other secret jails in Poland and Hungary.
Mohammed's lawyer has described his client as 'exceptionally intelligent'.
