23/03/2012 11:02 GMT | Updated 23/05/2012 06:12 BST

David Tennant Tells New Doctor Who Companion Jenna-Louise Coleman: 'Watch Your Back'

David Tennant has issued a stern warning to Doctor Who newbie Jenna-Louise Coleman , urging the actress to "watch your back" as she's catapulted to fame.

The former Emmerdale star has been picked to play Time Lord Matt Smith's assistant in the next series of the cult sci-fi show, replacing Karen Gillan.

Tennant, who played Doctor Who from 2005 to 2010 before Smith took over, has congratulated Coleman on landing the coveted companion part - and urged her to "keep your nose clean" while she's in the spotlight.

He tells Digital Spy, "You're suddenly rocketed into a world of attention. You just need to watch your back a little bit, but it's wonderful and it's such an exciting thing to be starting out on.

"She'll have a brilliant time. I'm very jealous of (someone) starting out on that extraordinary journey."

Meanwhile, Smith has revealed he can't wait to start shooting scenes with his new leading lady.

He says, "I was part of the audition process where we met a number of wonderful actresses. But I think Jenna responded to Steven (Moffat)'s writing in the most interesting way. We're very excited to welcome her to the Doctor Who family."

And Coleman is delighted with her new job, insisting: "I am beyond excited. I can't wait to get cracking."

Jenna-Louise Coleman, Dr Who’s new companion...

Jenna-Louise Coleman