Walliams shared a photograph of himself and Dame Barbara, 80, seated next to each other as he wraps his left arm around her and uses his other to hold her hand.
He wrote on Instagram: “Afternoon tea with the woman of my dreams ever since I was a boy, the unbreakable Dame Barbara Windsor.”
In the photograph, the former EastEnders star is resting her head on Walliams’ shoulder and the pair are smiling widely.
Walliams shared the same picture on Twitter, writing: “Afternoon tea with a legend.”
In May, Dame Barbara’s husband Scott Mitchell said she had been taking medication to manage her condition but that symptoms had worsened in recent weeks.