USS St. Simon (CVE-51) (originally AVG-51 then later ACV-51), an escort aircraft carrier originally classified as an auxiliary aircraft carrier, was laid down on 26 April 1943 at Tacoma, Washington, by the Seattle-Tacoma Shipbuilding Corporation, under a Maritime Commission contract (MC hull 262); reclassified as an escort aircraft carrier, CVE-51, on 15 July 1943; launched on 9 September 1943; sponsored by Mrs. R. H. Lewis, the wife of Major General R. H. Lewis, Commanding General, Northwestern Sector, Fort Lewis, Washington; assigned to the Commercial Iron Works, Portland, Oregon, for the completion of construction; and delivered to the Royal Navy, under lend-lease, on 31 December 1943.

Renamed HMS Arbiter (D31) (while being carried on the United States' Naval Vessel Register with the classification BCVE-51), the escort carrier served in the Royal Navy for the duration of World War II.

Converted to the cargo ship Coracero, the former escort carrier served under two more names, President Macapagal from 1965 to 1972 and Lucky Two in 1972 before she was scrapped in Kaohsiung, Taiwan, in 1972.

[2][4][5][6] Following commissioning, Arbiter underwent modification for Royal Navy service at Esquimalt in Western Canada,[a] before transferring to the East coast of the United States via the Panama Canal.

[7] In September 1944, Arbiter entered refit at Belfast,[2] with changes including a modified fuel system incorporating the lessons on the loss of the carrier HMS Dasher from an internal explosion in 1943.

[2][9] After the end of the war against Japan, she returned to Australia, where she was used for deck landing training for ex-RAAF pilots transferred to the nascent Australian Fleet Air Arm.