Additionally, "UB-27" was sent out on 20 May with instructions to work its way into the Firth of Forth past May Island. "U-46" was ordered to patrol the coast of Sunderland, which had been chosen for the diversionary attack, but because of engine problems it was unable to leave port and "U-47" was diverted to this task. On 13 May, "U-72" was sent to lay mines in the Firth of Forth; on the 23rd, "U-74" departed to lay mines in the Moray Firth; and on the 24th, "U-75" was dispatched similarly west of the Orkney Islands. "UB-21" and "UB-22" were sent to patrol the Humber, where (incorrect) reports had suggested the presence of British warships. "U-22", "U-46" and "U-67" were positioned north of Terschelling to protect against intervention by British light forces stationed at Harwich.