Naismith mansion

Joshua Naismith lived at a mansion with his daughter Abigail. The mansion was located within the outskirts of London and was the location of the Immortality Gate.

History
Joshua Naismith had his own private army which operated as the mansion's security. (TV: The End of Time)

After Naismith acquired the Immortality Gate following the collapse of Torchwood One, (TV: Doomsday) he stored it at his mansion. He employed several technicians to operate on the Gate. Collins, one of Naismith's technical staff, acted as the Gate's test subject. The Gate mended her burn scars from her childhood. Aware of its capabilities, Naismith wished to use the Gate in order to make his daughter Abigail immortal.

Also among Naismith's technical staff at the mansion were Addams and Rossiter, who unbeknownst to Naismith were actually a Vinvocci salvage team posing as human, hoping to retrieve the Gate. Naismith also employed butlers and waiting staff at the mansion, such as Danes.

Discovering had returned, Naismith brought him to his mansion in the hopes of fully repairing the Gate. However, this inadvertantly resulted in the creation of the Master Race, as the Master used the Gate for his own purpose. Following this, the mansion operated as the Master's own headquarters, and due to the presence of the Gate, was also used to "tether" the Time Lords from the Time War. The mansion was partially damaged during these events, with the Tenth Doctor smashing through its glass ceiling after jumping from the Hesperus spacecraft in his rush to prevent the Time Lords' plan.

Following the restoration of the human race and the return of the Time Lords back into the Time War, the now abandoned mansion was the location of the Tenth Doctor's cause of death. The Doctor released Wilfred Mott from the Gate's radiation control booth, with the Doctor being subject to the Gate's overloaded radiation burst, which ultimately caused his regeneration.

The Naismiths and their staff had fled the mansion in the chaos. Both Naismiths were later imprisoned for "crimes undisclosed", losing ownership of the mansion as a result. (TV: The End of Time)

Years later, a chair from the Naismith mansion was part of the Black Archive's inventory. (TV: The Day of the Doctor)

In an alternate timeline, the Tenth Doctor did not save Wilfred at the Naismith mansion, instead going on to conquer the universe as the "Time Lord Victorious". (COMIC: Four Doctors)