The Cardiff cyclist, 33, who won the world's premier race in 2018, made the announcement on social media.

On Instagram, he posted a picture of his son's feet and wrote: "Yesterday was our four-year wedding anniversary and earlier this week we welcomed another Thomas into the family.

"Sa and our little boy doing great #ifcarlsbergdidweeks".

Thomas was part of the Great Britain team who took part in the World Championships in Yorkshire last weekend.

He then travelled back to Cardiff to be with Sara, 27, for the birth of their first child at the University Hospital of Wales.

British Cycling replied to his tweet saying congratulations, while presenter Gethin Jones commented on his Instagram post congratulating the couple in Welsh - "llongyfarchiadau".

Fellow cyclist Mark Cavendish, added: "Beautiful news."

Geraint Thomas after winning the Tour de France in 2018

In December, Thomas was voted the BBC Sports Personality of the Year.

In June, he had a bad crash while hoping to defend his Tour de France title at the Tour of Switzerland, but admits he was "lucky" to avoid serious injury.

The couple spend most of the year living in Monaco where Team Ineos rider Thomas trains but returned to Wales to be with their families for the birth.

They married four years ago at St Tewdrics House, near Chepstow - and liked their wedding so much they bought the venue, which Sara manages along with her parents.