OLYMPIAN Sir Chris Hoy has said he is "amazed, delighted and a little shocked" after the birth of his son two months early.

Callum David Robert Hoy was born at 2pm yesterday at 29 weeks. He had been due in December, but the baby and his mother Sarra, Sir Chris's lawyer wife, are doing well.

The former athlete, the most decorated Olympic cyclist of all time with six golds, tweeted a picture of his child.

Sir Chris, 38, also told his 610,000 followers on the micro-blogging site they were pleased with how things were going.

The rider quit the spot last year to take up a career in motorsport. He thanked medical staff for their "incredible" help.

The Edinburgh-born star tweeted: "Amazed, delighted & a little shocked to announce the birth of our beautiful baby son, Callum David Robert Hoy! Born at 29weeks, today at 2pm."

Moments later he shared a picture of tiny Callum's hand clutching his finger and added: "Although v. early days for wee Callum, he's doing well as is Sarra. Huge thanks to incredible medical staff."

Callum is believed to have been born in Manchester, where his parents live.

The former cyclist was flooded with messages congratulating him and his family.

Fellow Olympic gold-medallist Rebecca Adlington tweeted: "congratulations to you both! Hope Sarra is going well as well as baby Callum! Xx"

Sir Chris thanked everyone for their support and said: "Wow! Thanks for the huge load of messages coming in, I'm reading as many of them as I can to Sarra and Callum."

He previously spoke of his excitement about becoming a father for the first time.

"I think maybe I'm just blindly optimistic that it's going to be great fun and dead easy. I'm just very excited," he said.

"It's a very exciting period of my life and for me and Sarra, hopefully a wonderful experience."

"It's exciting and is going to be a whole different chapter in our lives now," he said. "It couldn't have come at a better time. Trying to be a dad and compete at the highest level in sport, I don't know how athletes - mums and dads - do it. Sport, to be fully committed at the highest level, takes every ounce of effort and energy you have got. You need all of that for being the parent of a newborn baby. I'm looking forward to being able to devote full attention to the baby and I'm sure Sarra is too."

They had opted not to find out the sex of their child.

Sir Chris had earlier revealed: "I just want, as every parent hopes, for a simple, easy birth and that baby and mum will be 100%. That is the crucial thing."

Sir Chris said he believes the "biggest compliment" he could give his father David and mother Carol, 64, is to try and be as good a parent to his children as they were to him. "I don't think there is anything I could have had or experienced as a child that would have made my childhood any happier," he said. "It's very nice to be in that position."

The birth came days after he spoke about how David, 68, had kick-started his sporting career by taking him to BMX races during his younger days.

"It wasn't ever in a pushy parent-syndrome way," he said. "My dad helped kick-start my sporting career by supporting, encouraging and taking me to BMX races all over the country - sometimes right down to the south coast of England.

Sir Chris plans to compete at the 24-hour Le Mans race in 2016, started his own bicycle company and is acting as an ambassador with various charities.