London

London is the capital city of England and Great Britain, and the main setting in both series of Hellsing.

General
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.

Originally a small settlement established by the Romans in 43 AD, London grew through the millennia 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.

In Hellsing
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.

The city of London appears frequently in the original anime series with the climatic 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 it 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 Millennium Organization, 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 vengeance 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, Millennium launched its war fleet of three advanced zeppelins, which presumably flew the thousands of miles from secret Nazi bunkers in Argentina to England. Upon arrival over British airspace, the numerous agents Millennium 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 Millennium fleet flew over the London, positioning itself in its center and then after a toast to the massacre they were about to perform, began bombarding the city in all directions with V-1 rockets.

After the initial bombardment had set vast swathes of London ablaze, Millennium 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 Vatican's forces and Archbishop Maxwell seemed to many of the surviving population to be holy salvation from Millennium's hordes. Unfortunately, Maxwell quickly dispelled their hopes by revealing his intentions; the Ninth Aerial Mobile Crusade was here to kill everyone - vampires and humans alike - in order to reclaim London for the Catholic Church. With that, over three thousand Papal Knights entered the city as their allied gunships opened fire on the streets below and Millennium's zeppelins.

Meanwhile, a detachment of Millennium's army led by First Lieutenant Zorin Blitz headed towards Hellsing Manor in a zeppelin, only to be shot down by Seras Victoria's Harkonnen II. With half of their number killed and most of their heavy artillery destroyed, the remaining vampires' advance was halted by a barrage of artillery fire and a field of claymore mines set up by the Wild Geese mercenaries. Unfortunately for the defenders, Zorin used her illusion powers to distract them while her minions used their combat knives as stepping stones to circumvent the minefield.

With the outer defenses passed, the vampires managed to breach the manor and kill most of the Wild Geese, forcing the remainder to barricade themselves in the conference room. Using the last of their rockets, the Millennium forces successfully breached the barricade, but Seras arrived and slaughtered them before they could finish off the mercenaries. When she confronted Zorin, however, the First Lieutenant trapped her in another illusion, leaving Seras unable to defend herself from a brutal assault that left her blinded, broken, and minus her left arm. Pip managed to save Seras before Zorin could finish her off, but ended up dying after being shot repeatedly by a surviving Nazi soldier and being impaled by Zorin's thrown scythe.

As Zorin summoned the remainder of her forces (left outside during the initial attack in case she needed reinforcements), Seras honored Pip's final wish and drank his blood, unlocking her full vampiric powers and replacing her lost arm with a tendril of shadow matter. Her newly-enhanced powers proved more than a match for Zorin's forces and Zorin herself, easily overcoming the latter's illusions before dragging her head against a wall at high speed, wearing it down to nothing. With the manor secure, Seras left the remaining two Wild Geese and headed for London to join the main battle.

The main battle sees Alucard and Alexander Anderson facing off, with the latter's power completely released, summoning his own army of souls he had taken over the years. Anderson cuts them all down, making a line for Alucard, badly damaged in the process. Alucard taunts him, asking how he'll hope to win when he barely has two arms to fight with, but Anderson preserves. To Alucard's disappointment, anger, and sadness however, the Priest turns himself into a monster using Helena's Nail, snatching away Alucard's want and will to be defeated by a human. Enraged, Alucard destroys Anderson, who says his final goodbyes to Yumiko Takagi and Heinkel Wolfe.

Suddenly, a vampiric Walter C. Dornez charges in the middle of the heartfelt moment and challenges Alucard, revealing he was a mole for Millennium all along. He battles Alucard and actually has the edge on the battle for a while, until his new body starts to fail him and he starts to regress even further in age. Alucard, assuming his female form, begins to pummel Walter and defeats him, lauding that Integra and Seras will never be his again where they were before.

Integra and Seras then head for The Major, Seras dueling and defeating The Captain while Integra puts an end to the cyborg.