Diagon Alley was the first fatality of the second war. When Voldemort's Death Eaters marched through, from Knockturn Alley down to the Leaky Cauldron, every shop-front shuddered as if the air bracketing it had suddenly shoved forward. As if they were being viced together, atom to atom. Flourish and Blotts buckled, coughing quills out from the mouth of the doorway; Ollivanders shivered and shrugged and shook into rubble, raw magic bleeding out between stones. Shoppers spilled out, into the streets, waving their hands and fumbling their spells, unprepared for combat and dying without a curse on their lips. The Death Eaters finished off any in their path with a deft avada kedavra, or else a lingering crucio, but the remnants of buildings still held survivors when the army Apparated to Malfoy Manor and locked Diagon Alley down as a blank zone on the map.
Muggle Londoners living nearby heard screaming, desperate pleas for help wailing through the night as they tossed and turned and tried to sleep the noises away. Three people called the police, but there was nothing for the force to find. 'Are you sure you heard something real? Not a CD?' We're sure, they said. There is an inimitable quality in a genuine human scream, something visceral that we hear in our guts and the small, dark places of our minds. 'We'll look into it. Be alert.' But there's nothing to look into.
London sleeps with its lights on.
Harry Potter doesn't sleep at all.