Thames House
From Tardis Wiki, the free Doctor Who reference
Home of M15 in London's Vauxhall.
A special tank was built to house the 456 on the thirteenth floor. (TW: Children of Earth: Day Two)
The 456 arrived in Thames House in TW: Children of Earth: Day Three.
Thames House was the site of Ianto Jones' death. The 456 released a virus which killed everyone the building, except Dekker who survived by wearing a hazard suit. (TW: Children of Earth: Day Four)