The prospect of an unpredictable new version of Top Gear under Chris Evans is "terrifying", the head of BBC Two has admitted, saying "you don't quite know what's going to happen next".
Kim Shillinglaw, the controller of BBC Two, said there would be significant changes to the show under Evans, who takes over from Jeremy Clarkson, James May and Richard Hammond.
Among the "really interesting" changes will see Dunsfold track supersized and a changing line-up of presenters still being masterminded by Evans.
Calling him "incredibly spontaneous", she said viewers would never know what would happen next.
Speaking at the Edinburgh International TV Festival, Shillinglaw also spoke about the ending of Clarkson's contract, saying it was "very sad" and exposed the "human frailties" of working in television.
When asked about the new series of Top Gear under Evans, she said she is "so excited and of course terrified".
"I really can't think of a person that better combines two things I think are really central to Top Gear: one is an absolute genuine passion for cars, but also being incredibly spontaneous, incredibly surprising.
"You don't quite know what's going to happen next.
"Watching someone who has that is always fantastic telly."
She added: "It's going to be different. There will be continuity, but it will be really different.
"Dunsfold is looking quite interesting, the presenter line-up is going to be a bit different.
"So there will be some changes to the show. It's scary but it's really exciting."
When asked about Clarkson, who famously left the BBC after a "fracas" which saw him punch a producer, she said: "For me, I think it was a very sad episode in lots of ways.
"The biggest reminder is that for all this is telly, this is business, this is competitive industry, at the end of the day it's about human beings. It was just a very human situation.
"I am and always will be fond of Jeremy and James and Richard, and have great respect for their craft skills.
"I think it was just very very sad, the way in which the human frailties I think you have to, as a person, be respectful and understanding of became part of the story.
"To get to a point where it wasn't something that as the BBC was acceptable. I don't think any organisation would find it acceptable.
"And for me the biggest story is that sometimes human beings are bigger than telly."
Further announcements about the new presenting line-up, and the outcome of the thousands of fan audition tapes received from around the world, are due later this year.
AT A GLANCE
Reportedly £1 million in 2013 (plus £13 million from BBC joint venture and dividends)
Started out as a motoring columnist. Top Gear presenter since 1988
Quote: "[Top Gear] was my baby, I adored it, I paid attention to every little bit"
Salary: Reported three-year contract worth £3 million
Car credentials: Has one of the most prestigious car collections in Britain, including a £12 million 1963 Ferrari 250 GTO
Quote: "I will do everything I possibly can to respect what has gone on before and take the show forward"