The Midnight Mayor - Or, the Inauguration of Matthew Swift (Electronic book text)

It's said that if the ravens ever leave the Tower of London, then the Tower will crumble and the kingdom will fall. Resurrected sorcerer Matthew Swift is about to discover that this isn't so far from the truth. . .
One by one, the protective magical wards that guard the city are falling: the London Wall defiled with cryptic graffiti, the ravens found dead at the Tower, the London Stone destroyed. This is not good news. This array of supernatural defenses - a mix of international tourist attractions and forgotten urban legends - formed a formidable magical shield, one that could protect London from the greatest threat it has ever known. But what could be so dangerous as to threaten an entire city?
Against his better judgment, Matthew Swift is about to find out. And if he's lucky, he might just live long enough to do something about it . . .