Stone heart Trilogy, Book One, The Stoneheart by Fletcher, Charlie

A city has many lives and layers. London has more than most. Not all the layers are underground, and not all the lives belong to the living.

Twelve-year-old George Chapman is about to find this out the hard way. When, in a tiny act of rebellion, George breaks the head from a stone dragon outside the Natural History Museum, he awakes an ancient power. This power has been dormant for centuries but the results are instant and terrifying: A stone Pterodactyl unpeels from the wall and starts chasing George. He runs for his life but it seems that no one can see what he’s running from. No one, except Edie, who is also trapped in this strange world.

And this is just the beginning as the statues of London awake…