The little voice in the back of Sirius's brain is telling him that now is not a good time for a joke. He needs to stay focused on the task at hand.

"There are ways around that. If we can get through there, we'll have a bit more of the element of surprise than barging through the front. Unless he's got friends?"

The grandfather, though it was weird to consider him that, seemed to know what he was doing. This seemed calculated.