David Tennant thinks portraying the Time Lord in 'Doctor Who' "changed" his life.

David Tennant

David Tennant

The 45-year-old actor played the iconic titular character in the sci-fi series from 2005 until 2010 and has admitted the next person to take on the leading role later this year is in for a treat because the show opened up new exciting avenues for him and his career.

Speaking on 'The Andrew Marr Show', he said: "It changes your life. It opens a lot of doors. I get to be in the West End and that's due in no small part because Doctor Who has brought me to a new audience. It's an undertaking."

However, the hunk has warned that it's a lot of pressure playing such a "big" part on national television and the actor who does take over from the current Time Lord Peter Capaldi - who has portrayed the role since 2013 - should prepare themselves mentally.

He explained: "It's pretty big. Because the show is so big and because people love it so much and so deeply. It's part of the national conversation. It's part of our cultural furniture. That's a huge honour to be in the middle of, but it's quite a responsibility."

It's not yet known who is being lined up to take over from Capaldi when he steps down as the time-travelling scientist but new boss Chris Chibnall has admitted he won't choose the person to play his Time Lord until the script has been written.

Viewers have called for a woman to be cast as the character and, although he's not giving it much thought at the moment, Chibnall - the creator of 'Broadchurch' and the miniseries 'Gracepoint'- has "a very clear sense" of what he wants.

He explained: "The creative possibilities are endless, but I have a very clear sense of what we're going to do, without even knowing who's going to play the part."

The 46-year-old television writer will take over from current show runner Steven Moffatt at the beginning of 2018 once Capaldi makes his final appearance as the time-travelling scientist in the Christmas special later this year.