New DR WHO DAVID TENNANT is terrified he'll flop as the iconic sci-fi time lord.

The Scottish actor replaces Christopher Ecclestone when the next series begins this month (DEC05) - and he feels the weight of expectation that comes with the long-running BBC show.

Tennant says, "I'm here to stay as long as I'm not sacked. It's a bit of a gamble.

"As long as I don't get sacked I'll do another series."