The Oscar-nominated actor, 48, is among residents in the Dartmouth Park area urging Camden Council to reject proposals to transform an existing property called Lamorna.
The Sherlock actor, 53, and his French actress girlfriend Rachel Benaissa, 30, have been dating for around three years but are rarely seen together in public.
Throughout most of 2024, Strictly has been embroiled in a scandal which all started when Sherlock actress Amanda Abbington accused her partner Giovanni Pernice of bullying.