The Lord Mayor of London, Magnus Crome, rules London with an iron fist. If he hadn't blown up along with London at the end of the book, he probably would have had Dr. Twix, the woman who makes the Stalkers, make him an actual iron fist, so that he could strangle babies and handicapped puppies with it.
Katherine tells us that Crome is different from past Lord Mayors. He's "thin as an old crow, and twice as gloomy" (5.19), and he dresses in Engineers' clothes, refusing to remove the Engineers' mark as previous mayors had done. Previous mayors were mayors of the people, all the people. Magnus Crome? He wants London to get better and stronger, and he'll crush anyone who gets in his way. Literally.
We won't mince words: Magnus is kind of insane. Even Valentine thinks the guy is "mad as a spoon" (34.10) at the end. (Mad spoons? What?) Magnus's plan for total domination doesn't stop with London. He wants to turn the world into a mortal engine that can fly around the galaxy eating other planets. Sure, Saturn looks tasty, but this guy is batty. However, he's simply following Municipal Darwinism to the letter. Where does survival of the fittest stop?
Crome is a control freak down to the smallest detail. When Katherine shows up for her appointment one minute early, Crome sits there and reads documents in silence for precisely sixty seconds before starting their meeting. Maybe now that London is rubble, Crome can get a job with Martha Stewart.
Plus, his public appearance is one of strictly business, like the front half of a mullet. "No pictures, no hangings or decorations of any kind, and the floor was bare metal" (14.5). We have no idea if he's got a secret party in the back, though, because we never get a glimpse of his personal life, or anything beyond his basic philosophy: London, strong. Raar. Magnus, buddy, there are other things in this world than just being strong. How can someone living in a world so technologically advanced be so primitive in mindset?
His last words before London mushroom-clouds from existence are, "I only wanted to help London! [...] I only wanted to make London strong!" (35.46). Was his heart actually in the right place, or was he just a power-hungry maniac?