Magnus Crome is the Lord Mayor of London in Mortal Engines. He has been mayor of the city for ten years and he is also head of the Guild of Engineers. Many Londoners believe that this is unfair and that he may put the priorities of his guild before those of London's three other guilds.
He is at least fifty and has a shiny, bald head (the engineers believe that hair is not necessary for survival). He has a red wheel, the symbol of the engineers, tattooed on his forehead, (this is the same for all engineers.) Unlike previous mayors, Crome doesn't wear the traditional mayoral robes, he opts to wear the white rubber coat that he wore during his time as an engineer.
Crome is a firm believer in Municipal Darwinism, and can be considered an extremist in dedication to the city way of life. Through MEDUSA, he sees the future of London as the dominant predator of the world, with cities not deliberately being eaten by his city being incinerated by MEDUSA. Likewise, cities of the Anti-Traction League will be devoured.
Apparently, Magnus Crome does acknowledge that the city hunting city way of life cannot go on forever. However, he believes that after prey is exhausted, London will burrow into the Earth, create engines powered by the molten core of the planet, and move the planet from its original orbit and devour the other planets, the sun itself and eventually the whole star systems.
He is responsible for having his men capturing Hester Shaw, who is intent on sabotaging MEDUSA. When MEDUSA is about to explode due to sabotage, some sympathy can be felt for the Lord Mayor. He proclaims that he "only wanted to make London strong". He dies, along with most of London, in the resulting explosion.