London

And then suddenly something fell out of the sky and exploded in the market square, and there was a black gash in the deck and the men he had been watching weren’t there any more. Others came running with buckets and fire extinguishers. “Airship! Airship! Airship!” someone was shouting, and then there were more rushing things and buildings were exploding all over the suburb, with people flung tumbling high up into the air like mad acrobats.

Chapter 19: Sea of Kazhak, Mortal Engines

The ship firing these rockets is the Jenny Hanniver, piloted by Anna Fang. The same ship fires on a London Goshawk in the second half of the durability feat involving rockets.