JASON Kenny's mum says she's 'thrilled' to be becoming a grandma, after her cycling hero son announced he is due to become a father.

Lorraine Kenny admitted that she'd struggled keeping news of daughter-in-law Laura's pregnancy a secret, until Britain's most successful female Olympian posted a cryptic photograph of two adult bikes next to a child's bike on Instagram on Tuesday.

The news was later confirmed by the golden couple's agent, prompting thousands of congratulatory messages on social media, as well as a witty response from Jason himself.

Lorraine said: "We're all absolutely thrilled to be expecting a baby in the family.

"I honestly don't know how I haven't spilled the beans before now.

"Laura has had a brilliant start to her pregnancy. We hope this continues and we can't wait to welcome the baby later in the year."

Jason offered a humorous response to Laura's bike picture, tweeting a photo of the pamphlet titled ‘So You’ve Ruined Your Life’, which was handed to a pregnant Marge in an episode of The Simpsons.

Jason, 28, who turned on Bolton's Christmas lights last year alongside Laura, 24, said: “I wondered why this leaflet came through the post.”

Many will now be hoping that the Farnworth Flyer digs out his old stabilisers - with bookies already taking bets on whether junior Kenny will become and Olympic medalist one day.

The couple's relationship became public at the London 2012 Olympics, where they each won two gold medals in the velodrome and were pictured kissing at the beach volleyball competition at Horse Guards Parade.

At the time it was joked that British Cycling had embarked upon a breeding programme.

The couple were asked about the prospect of becoming parents at last August's Rio Olympics, when Jason won three golds to move level with Sir Chris Hoy on six golds as Britain's most successful Olympian.

Speaking in Rio, after two more golds took her Olympic tally to four, Laura, said: "We haven't exactly thought about it.

"I guess I am still quite young. I only put it out there because everybody kept going on about it.

"So I was just like: 'It could be the best omnium rider in the world, couldn't it? Bit of sprint, bit of endurance. You never know. 20-something years down the line, you never know."

With pregnancy having arrived significantly earlier, Laura will now take an enforced break from the bike, missing April's Track World Championships in Hong Kong.

Meanwhile, bookmakers William Hill are offering odds of 50 to one that the couple’s first-born will win an Olympic medal.

Spokesman for William Hill, Joe Crilly, said: “Laura Trott famously tweeted during the Olympics that any child they had would be blessed in the gene department, and given that we have previously offered 500/1 for Kai Rooney to play for England and 100/1 for Jaden Agassi to win a Grand Slam, we think she may be right.

“Despite the fact that the announcement was only made on Valentine’s Day, we have already been inundated with requests for the long term wager.”

Confirming the news on Valentine's Day after Laura's 12-week scan, the couple's agent, Luke Lloyd-Davies, said: "I can confirm that Laura Kenny is indeed pregnant and that she, Jason and their respective families are absolutely thrilled and delighted with the news.

"They very much appreciate all the kind wishes and messages of support that they have received already."