London

London is the capital city of England and Great Britain, and the main setting in both series of Hellsing. London is the home of the British government, Royal family and many famous landmarks including the Houses of Parliament, Tower Bridge, The Tower of London, St Paul's Cathedral and Trafalgar Square, most of which are purposely destroyed by Millennium in their invasion of Britain.

Origionally a small settlement established by the Romans in 43 AD, London grew through the millenia to become capital of England, Great Britain and the British Empire which, judging by quotes made by Sir Integra Fairbrook Windgate Hellsing and the Major, may still exist in some form in the Hellsing universe, or may simply be formal or metaphoric references.

The headquarters of the Hellsing Organization appear to be situated in the countryside some distance from London's outskirts, which could explain why Walter C. Dornez predicted that it would take many hours for reinforcements to arrive during The Valentine Brothers' Ghoul Army's siege on Hellsing.

Appearances
The city of London appears frequently in the original anime series with the climactic battle in the last episode between Alucard and Incognito taking place in The Tower of London and St Paul's Cathedral.

In the Hellsing: Ultimate OVA and the manga, London is only featured properly towards the end, when is invaded and devastated by Millennium, with many of its famous landmarks destroyed by V2 rockets and a large amount of it's population killed by the bombardment or Millennium soldiers. Many of London's population was also transformed into Ghouls.

Millenium's Invasion
In the manga and 2nd anime, it is revealed that the upsurge in vampire attacks on British soil is the work of the sadistic Nazi organization Millennium, which has been hiding in South America since the end of the war, and has been building a battalion of vampire soldiers to reek revenge on those who defeated them, singling out Britain as their first (perhaps only) target, so as to destroy the Hellsing Organization and Alucard, both out of vengence for the part they played in destroying their earlier facility in Warsaw, and to remove them as a threat to their plans.

After Hellsing's attempt to destroy them in Brazil proved largly fruitless, Millenium launched its war fleet of three advanced zepplins, which persumably flew the thousands of miles from South America to Western Europe. Upon arrival over British airspace, the numerous agents Millenium had placed in Britain sprang into action, attacking military instillations across the country or severing communications between bases, leaving the British Military crippled and unable to carry out any defense plans they had formulated.

The oblivious public watched in awe as the Millenium fleet flew over the London, positioning itself in its centre and then after a toast to the massacre they were about to perform, began bombarding the city in all directions with V2 rockets.

After the initial bombardment had set vast swathes of London ablaze, Millenium deployed its main attack force via catapult-like launch systems, dropping them into the city in their hundreds, where they began massacring and feeding off any civilians they found and wiping out pockets of military or police resistance.

The Battle of London
The arrival of the Reconquista and Bishop Maxwell seemed to many of the surviving population to be holy salvation from Millenium's hordes.