The former X Factor star and her model beau got into the Valentine's Day spirit 24 hours early by puckering up at the famous London station and didn't appear to mind who was watching while they smooched.
Dressed in a chic cream and black outfit with red heels, Diana embraced the romantic moment with her man and even lifted her leg as they kissed in true Hollywood style.
Craig was suited up for the occasion in a grey ensemble and seemed to be more focused on snuggling up to Diana than looking at the camera.
Apparently the brown-haired model is pulling out all the stops this year to give his lady a Valentine's to remember. Aww!
First, Craig plans to take Diana out for a fancy meal and then he is planning to whisk her away on a romantic holiday. Lucky girl!
The couple were putting on a very public display of affection this afternoon at St Pancras to launch a new competition for lastminute.com, encouraging fellow couples to share their best kiss at the kissing statue for a chance to win a Valentine's Night in Paris.
But we're not sure how many people would be as brave and bold as Diana and Craig.
The smitten twosome have been dating for three years and celebrated their anniversary two weeks ago with dinner at The Ivy.
As well as spending quality time with her love, Diana has been busy working on her music career and released her second album, Music to Make Boys Cry, last September.
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