William, the Earl of Strathearn, was quizzed about increasing his family when he visited the Irish Guards at their military base in Aldershot with wife Kate to mark St Patrick's Day.
The proud royal father, who is the regiment's Colonel, said during their day with the soldiers and officers that son George - who will be joining them on their trip to New Zealand and Australia next month - was crawling.
Kate presented sprigs of shamrocks to around 300 soldiers on parade and honoured the regimental mascot, Irish wolf hound Domhnall, with his own bunch of the well known plant.
Former Regimental Sergeant Major Ray Collister, 56, from Tamworth, lost no time in asking William if he was planning to add to his family after the ceremony.
William replied: "Maybe one day, one's enough at the moment."
The old soldier who served with the regiment for 25 years said after meeting the Duke that he asked him if he was planning another "Mick" - the affectionate nickname for the Irish Guards.
Mr Collister, who is wheelchair bound after suffering spinal injuries over the years, said: "I congratulated him on the birth of a new Mick and I wanted to know if he was planning any more baby Micks.
"William said 'when there's time'."
Hundreds of proud wives, girlfriends, and parents were seated on the parade square to enjoy the presentation of the shamrocks, a century-old tradition inaugurated in 1901 by Queen Alexandra, the wife of Edward VII.
In the past, the role was famously carried out by the Queen Mother, but also performed by the Princess Royal and many others over the years, in many different countries.
In keeping with the day, the Duchess wore a stylish emerald green coat by Hobbs and matching hat by Gina Foster, and wore a gold Cartier Irish Guards brooch, a Royal Family heirloom also worn by the Queen Mother.
At the start of the ceremony William was one the first to receive a shamrock from his wife and, following tradition, tucked it under the regimental star on the front of his cap.
Before the royal couple were around 300 soldiers - the majority from the Irish Guards. but they were joined on parade by a company of reserve soldiers from the London Regiment with whom they are paired under the new Army2020 restructuring process.
The event is the one day when the entire regimental family comes together and there were veterans on the parade ground proudly displaying their medals on their suits and a small contingent of cadets.
Kate, who wore a large shamrock sprig on her left shoulder, presented baskets of the plant to officers and warrant officers, who handed them out amongst the soldiers.
Officers received their sprigs from the Duchess and she chatted for a while to each man in turn.
After the presentation of the shamrocks, the royal couple went to the cookhouse, where dozens of guardsmen were sitting down to lunch. They accepted a toast in their honour, with the Duke and Duchess drinking port while most of the servicemen downed Guinness and Fosters lager.
They chatted to Guardsman Glenn Tierney, 25, who said afterwards they talked about the win the Duke's football team Aston Villa enjoyed over Manchester City.
He said: "It was amazing to meet them. I joked to William it's nice to see a Villa fan with a smile on his face.
"I asked them all about George, I'm nosey like that. He said he's doing really well and he's busy crawling and eating.
"They said they're very busy sorting everything out for taking him to Australia. They said they were excited and looking forward to it."
During the visit, William also chatted to Ray Kidd, 72, a former regimental cook, who said: "I asked him if he'd bring George next time and he said 'Yes, that's a good idea. I'll get him fitted for a uniform'."