Merlin: The Return
(2000)

Mordred is slain when Arthur chucks Excalibur at him where upon it impales him right through his chest. On his destruction Merlin (Rik Mayall) uses the stone circle to send himself, Guinevere, Arthur and his knights back to their own time, though not before Arthur knights Richie Gould and drags Dr Joan Maxwell (Tia Carrere) back into the past with them. Lancelot however leaves the stone circle to stay in the present.

Thanks ND Woods!