"London", along with battleships "Implacable", "Queen", and "Prince of Wales", was transferred to the 2nd Detached Squadron, organised to reinforce the Italian Navy in the Adriatic Sea when Italy declared war on Austria-Hungary. She was based at Taranto, Italy, and underwent a refit at Gibraltar in October 1915 during her Adriatic service. In October 1916, "London" returned to the United Kingdom, paid off at Devonport Dockyard to provide crews for antisubmarine vessels, and was laid up. While inactive, she underwent a refit in 1916–1917. The work included removing her main deck 6-inch guns and the upper deck 12-pounder guns and moving four of the 6-inch weapons to the upper deck battery where the 12-pounder guns had been located.