Cable laid from Oban to Newfoundland . Oban , Argyll : The link - up of the first Transatlantic cable from Newfoundland to a point south of Oban was completed today when the final splice between the two cables was made on board the HMTS Monarch . For this link - up the Monarch has been laying the longest submarine telephone cable ever to have been laid on one operation . Photo shows ; The Monarch dropping the cable after completing the link - up . 26 September 1955 *** Local Caption *** 305398