The brunette beauty met the former Gladiator 12 weeks ago, and after a whirlwind romance, Kelly said yes when David proposed.
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"Lovely Weekend in Wigan meeting my New extended Family! Such happy times and excited to share my life with the most wonderful man I've ever met", Kelly captioned the picture, which showed Kelly and David cuddled up together with a balloon bearing the word engaged.
Rumours had been swirling for several days that David had propsed, but Kelly arrived at Heathrow airport earlier this week with no engagement ring on her finger.
According to The Sun, Kelly was left dumbstruck by his proposal but reportedly took just three seconds to agree.
The two reportedly met on New Years Eve at Kelly’s bar in London, Steam & Rye.
Last month they were rumoured to have split after six weeks of dating, during which time they spent visited Miami for a beach holiday and spent Valentine’s Day in Los Angeles.
Kelly and David
Speaking to Now magazine about their introduction, David, 27, said: "I got chatting to her but I didn't think it was going to go anywhere. Kelly's a nice girl, I like her company. She's a great person and the best thing about it was we just clicked, so I've been spending a lot of time with her."
Earlier in February, Kelly was once again showing off her famous curves in a series of saucy images for New Look, modelling her new racy range of Valentine's lingerie which she had designed herself.
The 34-year-old was previously engaged to Hollywood Billy Zane but broke off the engagement in 2008. Late in 2013, model Kelly was spotted having dinner with Welsh TV presenter Gethin Jones, who had previously been engaged to Kelly’s friend Katherine Jenkins.