Thames House

Thames House was the headquarters of MI5, located in London. (TV: Children of Earth: Day Four)

When the 456 returned to Earth in 2009, a special tank was built to house their ambassador on the thirteenth floor. (TV: Children of Earth: Day Two) Prior to their arrival, all the children of the Earth pointed in the direction of Thames House. When the 456 ambassador arrived, a pillar of fire came down out of the sky and into the tank before disappearing, leaving the ambassador behind. The pillar of fire appeared to do no damage to Thames House despite passing through at the very least, the roof. (TV: Children of Earth: Day Three)

Jack Harkness and Ianto Jones confronted the 456 ambassador at Thames House. The 456 released a virus which killed everyone in the building, except Dekker, who survived by wearing a hazard suit. (TV: Children of Earth: Day Four)

After Jack attacked the 456 with a reconstitution wave, the 456 ambassador began writhing in its tank in Thames House before apparently violently exploding. Before the 456's apparent death could be investigated, its remains were removed from Thames House in another pillar of fire. (TV: Children of Earth: Day Five)