The two stars became good friends while both competing in last year's dancing competition and on seeing Steve's happy news, Mark was quick to send his well-wishes.
The former TOWIE star said: "Congratulations guys !! Loads of love x @SteveBackshall @Helenglovergb."
Steve had announced to his followers he is set to wed, yesterday (16 September).
The 42-year-old popped the question to girlfriend and Olympic rower Helen Glover while the pair were watching the sunset in the Namib Desert. Can you get any more romantic?
Revealing his engagement joy, Steve shared a slew of photos of himself and his now-fiancée after his proposal. He told fans: "Sunset in the Namib desert, I asked the most beautiful girl in the world to marry me & she said yes! @Helenglovergb."
Helen too made sure to mark the moment on social media, giving us all a good look at her new diamond accessory. Showing off her ring, she tweeted: "Happiest girl in the world!!! Most romantic moment ever as the sun was setting in Namibia @SteveBackshall."
Steve's proposal came as the couple were tracking animals in Africa. Now that's definitely a story to tell!
On seeing the couple's tweets, Mark wasn't the only contestant from Strictly's last series to congratulate Steve and Helen.
Rugby pro Thom Evans told his pal and his wife-to-be he was "so happy for them both", while MasterChef's Greg Wallace tweeted Steve to say: "Go mate!!!"
He jokingly replied: "Thanks Greg! We're both bouncing off the walls... Well, the sand dunes!"
Steve danced alongside professional Ola Jordan during his time on Strictly, making it to week nine of the competition. He joined the likes of Mark, Thom, Pixie Lott, Frankie Bridge and EastEnders' Jake Wood on the show.
The series was eventually won by X Factor's new host Caroline Flack.
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