And he proved to be one of the morning show's most popular guests as Kate's colleagues Andrew Castle and Emma Crosby both clamoured to hold the little boy during his visit.
Despite his mum's nerves, Billy – sporting a thatch of brown hair - was perfectly behaved as Andrew and Emma cooed over him, even managing a smile for his first television appearance.
It wasn't just the audience and the presenters who turned to putty over the adorable baby.
According to his proud mum, his big sister Darcey – Kate's three year old daughter with husband Derek Draper – is just as smitten.
Darcey's obsessed with him," revealed the 42-year-old. "She's a proper little mummy and whenever my back is turned he gets covered in gold stars and stickers – he looks like Blackpool Illuminations."
Kate, who will return to the breakfast show from her maternity leave in November, also admitted she would be quite keen to have a third child.
"I must admit I do quite fancy it," she said. "I feel like I have got into the rhythm now!"