[L does the same by way of the fire escape. He's fairly certain that it's under surveillance, expecting nothing less from a former successor's premises. He absolutely expects thoroughness; he just doesn't expect care. Once it's clear that he's not here to sabotage or hurt anything, except perhaps himself, whoever might be watching will probably glance away.

He thinks he can live with people glancing away from him.

Though his going isn't particularly swift, it takes him two or three minutes tops to reach the roof, and the second he touches the helicopter, his face lights up. He won't know if it's his until he is actually inside and is able to check whether his 37-digit passcode is accepted to even fire the thing up, but he's excited, nonetheless.]