Dr. Yearling, and a group of soldiers, managed to infiltrate the Chimeran hub tower during the Battle of London. He mentions that that the interior supports make the structure extremely resilient to external pressure. He also comments how the temperature inside the tower is extremely cold causing several nosebleeds amongst his men. He also comments how the structure is easily capable of holding creatures larger than Widowmakers and Angels.
It is unknown whether Yearling died or not in the London Tower. He could had been capture or killed by the Chimera, or had fortunately escape.