This happened during the recording sessions of Sabbath's Sabotage album over February and March 1975. The jam sessions with the fellow mates of Zep were recorded to which Tony Iommi is the owner of.
One Monday morning, Graham was driving Bill and Geezer down the A40 in the Rolls as usual, on the way back to London. They had just passed Oxford when a white Bentley convertible pulled alongside them, as Graham recalls:
The driver was Led Zeppelin's John Bonham, and his passenger was Rober