The Oz The Great And Powerful star and her Two And A Half Men actor boyfriend are living in the capital while Mila films new sci-fi movie Jupiter Ascending.
Mila and Ashton were spotted having lunch with the Queen's granddaughter Princess Beatrice and her American businessman boyfriend Dave Clark.
They ate at the hip Duck And Waffle restaurant on the 40th floor of Heron Tower in the city, before moving on to trendy Shoreditch bar Callooh Callay, where they apparently enjoyed tequila cocktails.
They finished off their tour of the capital at new gastro pub The John Salt bar in Islington, North London.
John Salt boss Leigh Gillson told The Sun newspaper: "They asked for our best speciality dish. We gave them deep fried banana in caramel."
Mila and Ashton have been friends for 14 years after working together on That 70s Show and began dating last year following his split from wife Demi Moore.