London is a real world city in Europe, and the capital city of England. It has borne witness to several great giant monster battles, and the military has engaged several monsters near it. London also features in several games, most notably Godzilla: Destroy All Monsters Melee, Godzilla: Save the Earth and Godzilla Unleashed.
Gorgo is transported here by humans from off the coast of Ireland. Ogra, his mother, travels to London to find him, and a battle between Ogra and the British Military ensues. Once Ogra breaks down the defenses surrounding Gorgo's enclosure and reunites with her child, the two leave the city peacefully, having thoroughly broken it into ruins.
In the Monster Wars Trilogy, the Tachyon Aliens send the mind controlled Godzilla, Cyber-Godzilla and several of Godzilla's previously defeated foes they had recovered to attack major cities around the world and force humanity to deplete their weaponry in preparation for the Tachyon's invasion force. One of Godzilla's enemies, Crustaceous Rex, is sent to attack London - traveling up the Thames and destroying the Tower Bridge as it enters the city; later destroying Big Ben. At the end of the Monster Wars with the Tachyon's defeat, Crustaceous Rex is one of the few monsters to survive, with its unconscious body seen near the ruins of Westminster.
London is shown in flashback at the beginning of the film when Haruo is explaining how monsters began appearing after the last summer of the 20th century, with London coming under attack by the monster Dogora. Sometime later, ships belonging to the Bilasaludo appeared over Westminster - with the Bilasaludo's leader Dolu-do explaining that they were seeking immigration to Earth after their homeworld was destroyed when it was sucked into a black hole; promising to help elimate Godzilla if humanity accepted.