Tennant's new 'Who' companion announced

Newcomer Freema Agyeman has been named as Billie Piper's replacement on Doctor Who.

Agyeman will join as Martha Jones - described as "the perfect foil for the Doctor" - from the third series of the show, due to air early next year.

"Auditioning with David in secret down in Cardiff was unbelievable, but I never in my wildest dreams thought I'd actually become the new companion," she said. "Billie rightfully built up an amazing fan base and she will be missed, but I hope the fans are willing to go on new adventures with me."

Agyeman, a 27-year-old Londoner, got the part after starring as Adeola in episode 12 of the current series.

"Watching her during filming confirmed what an exciting new talent she was, so under cover of darkness we called her back in to audition with David for the role of the new companion," said exec producer Russell T Davies.

"David and Freema are terrific together, and we're delighted to have chosen her to join the Doctor for more adventures in time and space."

He added: "Martha won't be featured in this year's Christmas special - we've got another surprise in store for that."