Rachel Cunliffe commented: "Brexit cat! It thought it wanted to be out, but on actually experiencing out it decided it very much wanted to be in."
Alistair Coleman said: "Apparently there's no way of opening the door from the outside, probably because cats wised up to door handles."
Larry has been a common sight in and around Number 10 since February 2011, when he became the first cat at the address to be given the title Chief Mouser.
The Downing Street website describes his day-to-day role as "greeting guests at the door", "inspecting security defences", and "testing antique furniture for napping quality".
He is also responsible for "contemplating a solution to the mouse occupancy of the house".