The innocuous smooch was given to 88-year-old Arthur Jones, per his request, at a tea party with Operation Overlord veterans in Arromanches-les-Bains in Normandy.
"Is it OK to kiss a princess?" the vet, who reportedly served in the battle's 7th Armored Division, asked the duchess as she sat down, according to the Mirror.
"Of course it is," she replied laughing. And that's when Jones kissed her on the cheek.
"As the prince [William] left, he said to me 'Were you chatting up my wife?' I told him I only gave her a kiss," Jones told the newspaper. "William laughed but I'm chuffed I've chatted up a princess. I bet I'll be picked up now and taken to the Tower of London."
The D-Day vet described the peck as "lovely" and said that he lost his wife 10 years ago so he didn't "get many opportunities for kisses any more."
"They gave up everything for our freedom," William, 31, said in a speech, according to Express. "They lie now together in the beautifully kept cemeteries that lie on the coast. … However, today is also about the young. It is vital for them that they remember the sacrifice made by so many. … It is vital that this sacrifice, and the reasons for this sacrifice, are never forgotten."
On May 29, the duchess put pregnancy rumors to rest (somewhat) by joining her husband at a distillery near Perth, Scotland. There, the royals, who are known as the Earl and Countess of Strathearn when they're in Scotland, had a whiskey-tasting during a tour of the Famous Grouse Distillery in Crieff.