The X Factor finalist, who is pregnant with her third child, proudly flaunted her rounded tummy in a figure-hugging black dress with sheer side panels as she attended the Parkinson’s UK fundraiser.
As she posed for photographers, Rebecca, 27, affectionately cradled her bump.
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The songstress was clearly delighted to be performing at the Royal Albert Hall as part of the Symfunny event, which was attended by the likes of Diana Vickers and TOWIE star Jessica Wright.
Earlier in the evening, she tweeted: "Performing at the royal albert hall today with an orchestra I can't wait xxx".
Later on, she used the social media site to express her gratitude. "I love my life god has truly blessed me #thankful x", wrote the expecting mum.
Rebecca's happy baby news came in April after a dramatic collapse live on Loose Women prompted her to take a pregnancy test.
The singer's suspicions were raised after she fainted during a performance on the daytime chat show. But she was left wondering what had happened when an initial pregnancy test showed negative
A few days later the news was confirmed, and she went on to share her excitement with fans on Twitter.
"Yes I am having a new lovely baby children are such a blessing and I'm grateful to god for my new little gift xx" wrote Rebecca, who is already a mum-of-two, to Lillie May and Karl.