Their lips touched just for a moment - but it was enough to send the crowd wild.
In one of the high points of the day, with the first hint of blue sky during the festivities, Prince William shyly planted a kiss on his newly-created Duchess - drawing huge cheers from the thousands of spectators watching around Buckingham Palace.
Then, as the wedding party watched the fly past - which featured a Lancaster, Spitfire and Hurricane aircraft followed by two Tornado and Typhoon fast jets - the crowd got another chance to see them puckering up.
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William leaned over and kissed his radiant bride, after asking her: "One more kiss?"
The show of intimacy marked a new era for the couple – who have never so as much as touched during a public event in the past.
Surrounded by her new family, including the Queen, Kate had looked overjoyed as she greeted well-wishers for the first time on the balcony.
She could clearly be seen saying "wow" when she saw the extraordinary numbers down below. The newlyweds appeared alone before they were joined by other senior royals and Kate's nearest and dearest.
Almost as soon as it began it was all over. William took his wife by the hand and led her back inside. Before they disappeared from view, the new royal star allowed herself a final backward glance, savouring the moment.
Don't forget to buy your souvenir edition of HELLO! with all the fantastic photos of the big day, on sale Sunday May 1