Alex Jones and Jason Manford's first appearance together on The One Show sofa drew in extra viewers.
Welsh presenter Alex's debut also proved a bigger draw than that of her predecessor Christine Bleakley's opening show three years ago.
Yesterday's eagerly-anticipated BBC One show was watched by an average of 4.5 million viewers and a 23.5 per cent share.
Christine, who has moved to ITV, was watched by 3.4 million (a 19.3 per cent share) when she replaced Myleene Klass on, coincidentally, the same date - August 16 - three years ago.
Jason and Alex's first show, which drew a mostly warm response from critics, also beat the 2009 average for the teatime programme - which was 4.3 million viewers and a 21.6 per cent share.
The show was also up on the equivalent Monday last year, August 17, which attracted 3.3 million (18.1 per cent).
A delighted Alex, 32, said: "We're over the moon that so many viewers tuned in to watch our first appearance on The One Show last night and hope they all enjoyed it as much as Jason and I did.
"We were nervous before the show of course but Whoopi really helped by being such a great guest."