New Top Gear host Chris Evans has described the role as "the most challenging thing I have ever done".
The broadcaster took the driving seat on the flagship BBC motoring show after Jeremy Clarkson was sacked for punching a producer.
Evans (49) said the move was even more significant than taking over from Terry Wogan as the Radio 2 breakfast show DJ.
He told Top Gear Magazine: "This is, without doubt, the most challenging thing I have ever done in my career.
"When I took over Terry's show, people kept saying I had big shoes to fill, and they're saying it again now."
He added: "By the way, Jeremy is very tall so they're even bigger shoes."
Evans said hosting Top Gear was similar to becoming the new Time Lord on Doctor Who.
He explained: "There have been 34 presenters before me, so it's a bit like Doctor Who - that's one way of looking at it."
The presenter has not yet confirmed what aspects of Top Gear will continue under his tenure.
"Nothing has to (stay in the show), but some things will," he said. "I can't tell you what precisely. But it would be silly to throw the baby out with the bath water."
There has been much speculation about who will replace Clarkson's co-presenters James May and Richard Hammond, with some suggestions there could be a female broadcaster.
Evans admitted it was "not the furthest thing away from my mind", but insisted the priority was recruiting the team who will make the programme.
He went on to reveal that the controversy over Clarkson's sacking had initially put him off the job.
"I honestly didn't think I'd get the phone call - I was amazed that I did, to be honest. I ruled myself out because I didn't want to be part of all the nonsense that was going on. But then the situation changed," he added.
"I was actually in the middle of preparing for TFI Friday and I talked to Will (Macdonald from the Channel 4 show) and he said 'Why would you not do this?' It wasn't 'Why would you do it?' but 'Why wouldn't you?'"