London - A London taxi driver was found guilty Friday of drugging and sexually assaulting 12 female passengers in the back of his car, for which he will be given a "substantial term of imprisonment," a court was told.

John Worboys, 51, gave the women champagne laced with sedatives after inviting them to celebrate an alleged large gambling win with him, Croyden Crown Court heard.

He had been preying on women he picked up between July 2007 and February 2008. Worboys denied the charges. He admitted offering the women drinks because he "craved female attention."

The court was told that many women were left with little memory of their ordeals and could only recall falling asleep.

"You must be under no illusion that this case requires and will get a very substantial term of imprisonment," the presiding judge said Friday. Worboys is due to be sentenced on April 21.