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, the 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 the 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.

Incognito and his Master executes their plan.
Incognito who murders Helena and devours her, goes to the Tower of London while his Master, who was later revealed to be one of the members of the Round Table, executes their plan to destroy England and Alucard by releasing the Egyptian deity known as Set. While Incognito's master orders the British Military to attack the Hellsing Organization who was there to get ready for a memorial, Incognito goes there and waits for Alucard to lure Integra, knowing that their battle will made her try to go there and stop them both. The Hellsing Organization goes inside the Tower of London and was attacked both by Incognito who released his Army of SAS Ghouls and the British Military and Chris Pickman, the captain was saved due to the arrival of Alucard. Seras Victoria, who failed to save Helena and stop the Hellsing Organization Military Forces to enter the Tower, witnessed Fargason's death and was in-raged, kills multiple Ghouls and later, engages in battle with Paul Wilson, Incognito's right hand man and a former SAS member. Alucard and Pickman wipes the SAS Ghouls and unfortunately, Pickman died but Alucard survived and enters the Castle to fight Incognito.

Alucard and Incognito.
Alucard engages in an intense battle with Incognito after entering the castle and shortly, Seras Victoria who has killed Paul, tries to save Alucard by giving him Jackal's magazine after he ran out of bullets and fell onto Incognito's clever trap, but instead gets heavily injured by Incognito's dark magic.

Incognito laughs and taunts Alucard and Alucard responds back angrily that he will send him to the bottom of Judecca, and that he should lick Satan's ass down there. He uses his telekinesis power to grab the Jackal's magazine and pulls the trigger at Incognito's head once again. But, Incognito simply phased his head becoming temporarily invulnerable, Incognito proceeds to telekinetically hurled the Jackal's bullets back at Alucard, giving him a "taste of his own blessed silver". As Alucard dies, he tells Seras that she should've listened to him. Seras tries to drink Alucard's blood, but it doesn't do anything.

The Final Battle between Alucard and Incognito.
As Incognito finished his ritual, Integra yells at Alucard, who was defeated by Incognito and "died" to release Level One. Incognito goes on top of the Tower of London and Set is released and starts to set London ablaze with Alexander Anderson, watching. Suddenly, London glows and a bright red pentagram appears out of nowhere, and the blood of the dead Hellsing Soldiers goes inside the Tower of London and Alucard gets revived. Alucard appears behind Incognito and mocks him, causing Incognito to get frustrated and annoyed and eventually transforms into Set and strikes Alucard. Alucard however, dodges it and is immediately impressed by Incognito's power. Incognito grows even more angry and strikes Alucard again, this time, Alucard holds its mouth open and Set proceeds to blast Alucard, to which, Alucard responds by mocking Incognito. Alucard then proceeds to summon Baskerville who later, bites onto Set and causes a huge purple shockwave that slices the London Bridge and shatters glasses. The shockwave also sent both Incognito and Alucard to the sky, and they both battles there for a while before impacting a Cathedral and lits up the entire building on fire from the inside. After a brief talk, Alucard and Incognito is prepared for a final standoff and both ran straight towards each other, shoots each other at point-blank range. Both got a huge chunk of their torso blown off, but it's nothing and both managed to heal. However, this turns out to be a trap set up by Alucard who was waiting to get near a huge cross made in silver and Set also merges onto Alucard, who melts the Silver cross and impales Incognito after creating a spear made in silver. Alucard reveals his true Identity to Incognito before impaling him again and hangs his body ontop of the destroyed cathedral.

Aftermath
London recovers and Incognito's Master was exposed and their fate was unknown and Integra was seen cuffed in a room with Alucard. Alucard grabs a glass of wine and crushes it, making his hand bleed. Alucard says that It's her choice if she wants to become a vampire like him.

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 largely 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 installations 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.