Prince Harry, 27, made an appearance yesterday at the WellChild Awards, organised by the charity of which he has been a patron since 2007.
A cheeky six-year-old Alex, suffering from Leukaemia, who was due to meet Prince Harry at the awards ceremony, had vowed on TV to bring up the 'cheeky issue' with the Prince, the Daily Mail reported.
Alex had promised his TV audience, he would say: "I'm glad you've got your clothes on Prince Harry."
But unfortunately for Alex, when the big moment came, Harry was one step ahead.
Before the youngster had time to follow his script, the Prince wagged his finger and said with a grin, "You keep looking up at your mum. It looks like you're dying to say something but you're worried she'll tell you off. I heard you were on ITV earlier and you said something cheeky, but let's not talk about that here."
Alex played ball and just tickled the prince with his toy penguin, as his mother, Debbie, watched proudly.
Yesterday's event was the first time the prince had been seen in public since he returned from Las Vegas.
The charity supports critically ill children.
Each year it presents awards to those it considers the bravest in Britain.
In his speech last night, the prince said: "All of you...
Are, quite frankly, too remarkable for me to adequately describe with mere words. But never one to be shy in coming forward, I'll give it a go."
The daily quoted sources as saying that the Prince was concerned about appearing in public after the media onslaught of the past few weeks but was more worried that the continuing rumpus over his "wild weekend" in Sin City would overshadow such a worthy occasion.
A source close to the Prince was quoted by the daily as saying,"Prince Harry is keen that what has happened does not overshadow what is going on today. He knows and understands there will be a lot of press interest because of recent events but just wants to focus on the children. That's why he is there."
The Royal Family was left reeling last month after US gossip website TMZ had published a grainy image of the prince, cavorting naked with a female friend in the Las Vegas hotel suite.