Severus had transfigured his clothes in what he had always worn when venturing into Muggle areas - black trousers, white button down shirt and a black jacket. He'd found over the years, from the 70s and into the 80s and 90s, that he could blend in wearing that, no matter what the current fashion was, especially as he got older. And even when he didn't blend in, he was still considered largely unremarkable.
Going on any sort of missions with Ron Weasley was, however, bizarre. He'd always had a great deal of respect for Molly (because what idiot wouldn't?) as well as Arthur (who was a shrewd and intelligent man underneath his fascination with Muggle paraphernalia) and, after they joined the Order, the two older boys, but Ron Weasley had been irritating as a student and frustrating in the last year as he'd been running around with Potter. However, the boy was now a man - and a man who looked at him with a mix of dislike and respect that he found both strange and amusing - and the change was a touch jarring.
"I know a place about a ten minute walk from the street entrance at St Mungos," he said with a grimace. "Death Eaters used it when they needed to... drop off someone without being seen. It didn't change in the twenty years I was involved with them so there is a reasonable chance it has not changed now."