New Countdown host Des Lynam has admitted he is anxious about taking over from the late Richard Whiteley on the Channel 4 daytime quiz show.
Des Lynam used to present the BBC's Match of the Day
Lynam told the Radio Times he will be a different host from the "national treasure and much loved" Whiteley, who died in June.
"I probably won't smile as much as Richard," he said.
Lynam, who is best known for hosting sports shows for the BBC and ITV, makes his debut on 31 October.
He said: "There's a little bit of anxiety because I'm following Richard Whiteley, who was a national treasure and much loved - and the only one who ever fronted the programme.
"It's the sort of thing I've never done before."
Lynam added that Whiteley had been "a great smiler".
"I smile inside more than outside, if you know what I mean," he said. "I hope people don't think I'm a bit too grim."
Vorderman and Whiteley's double act was a hit with afternoon viewers
Lynam's predecessor Whiteley presented Countdown for 23 years until his death aged 61 just days after having heart surgery.
His co-host Carol Vorderman, who has also been present since the show began, will now team up with Lynam, a personal friend.
The words and numbers game was the first show to air on Channel 4 when it began in 1982.
Since Lynam left ITV in 2004, he has fronted The World's Greatest Sporting Legend for Sky One, and hosted a Radio Five Live talk show.