"Upholder" was completed on 9 June 1990, followed by "Unseen" on 20 July 1991, "Ursula" on 8 May 1992 and "Unicorn" on 25 June 1993. Initially they were unable to fire torpedoes and the first three were refitted in 1992 and 1993 to have this fixed at a cost of £9 million. They were operating from (at Gosport), but with only four submarines the base was deemed uneconomic and they transferred to Devonport Naval Base. In their short period of service, the class operated mostly in the Atlantic Ocean, the Mediterranean and UK waters. The exception was "Unicorn", which completed a 6-month deployment east of Suez, completing operations and exercises in the Mediterranean, the Gulf of Oman and Indian Ocean and in the Persian Gulf.