Bille Piper has caused a stir by revealing she has nicknamed her ‘Dr Who’ co-star David Tennant “David Ten-Inch”.The actress has sparked speculation she has caught a glimpse of the dashing actor’s appendage on set by revealing her racy nickname.But although Billie, who plays the Time Lord’s companion Rose Tyler in the hit sci-fi series, knows the revelation will cause a stir, she is refusing to reveal whether or not she has actually seen his manhood. Billie said: “I have no basis or grounds for calling him that. I just find it funny.”David also has pet names for Billie, and calls his sexy sidekick “Carlos Carlos”, but the reason is unknown.Both Billie and David have signed up for a third series of the popular BBC series which returns to screens this weekend.