The fashion designer tweeted a photograph on Tuesday night (20 May) showing herself giving Tom a cuddle after bumping into him on a London night out.
"Nice to wish Tom Daley a happy birthday eve," she wrote.
Gemma got to know Tom earlier this year while she was competing on ITV diving show Splash!, where Olympic medallist Tom serves as the celebrity mentor.
At the time, Gemma described the athlete as an "absolute joy" to work with, saying: ""He's such a sweetie. He doesn't make you intimidated, he's encouraged me all the way. It is lovely to have had the pleasure of meeting him."
She even added: "I also think he looks like a young Bryan Ferry, which always helps. So it's all going swimmingly, as they say!"
Tom, meanwhile, was out last night for a pre-birthday meal with friends, including best friend Sophie Lee, who recently appeared alongside him on the ITV2 travel show Tom Daley Goes Global.
He celebrates his 20th birthday today, 21 May.
While Tom was out for dinner, Gemma was attending the Reveal Online Fashion Awards 2014 at the exclusive DSTRKT club in London, where she picked up the coveted Editor's Award recognising her contribution to fashion through her hugely successful plus size collection.
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All the pictures from Reveal's Online Fashion Awards below:
Copyright: WENN Daniel Deme