The 1922 Washington Naval Treaty, of which Britain was a signatory, did not ban submarines but it did ban their use against merchant ships, which was "X1"s unacknowledged purpose; its armament had been designed to successfully engage the classes of vessels likely to be escorting convoys, such as destroyers and frigates. Therefore, a certain amount of secrecy surrounded "X1", the government even going to the lengths of taking a national newspaper to court over its pictures of the new submarine following her launch, all copies of the paper being seized.