Sirius shrugged casually. Despite the danger of the whole situation, he always enjoyed it. It was a rush, the transformation, being with Moony, being canine in that sort of situation.
"Ready when you are," he said. "Still think it'd be more fun to just do it here in the flat." He was joking, mostly. Because even though Sirius was oftentimes laidback and casual, he knew the dangers that could occur if Remus, in his werewolf form, got loose in London.
He laughed a bit to himself then sobered.
"It'll be fine, Moony," he assured him. "We're with you. Whatever happens. You know that."