RMS Alcantara (1926)

RMS Alcantara was a Royal Mail Lines ocean liner that was built in Belfast in 1926. She served in the Second World War as first an armed merchant cruiser and then a troop ship, was returned to civilian service in 1948 and scrapped in 1958.

Building and civilian service
In the 1920s Harland & Wolff of Belfast built a pair of passenger liners for Royal Mail Lines, completing Asturias in 1925 and her sister ship Alcantara in 1926. The latter was named after Royal Mail Lines' previous SS Alcantara (1913) that had been sunk by a German armed merchant cruiser in 1916.

Each of the two new ships was powered by a pair of eight-cylinder four-stroke double-acting diesel engines built by Burmeister & Wain of Copenhagen, Denmark. These gave each ship a speed of about 16 kn. The ships worked Royal Mail Lines' liner route between Southampton and ports on the east coast of South America.

In 1934 Royal Mail Lines had both ships re-engined from diesel to steam. Each was fitted with three water tube boilers supplying superheated steam at 435 lbf/in2 to a set of six steam turbines that drove her twin propeller shafts by single reduction gearing. This increased each ship's nominal horsepower by 25% and increased their speed to about 19 kn.

Second World War service
In 1939 the Admiralty requisitioned Alcantara and Asturias and had each ship converted into an armed merchant cruiser. Each ship had one of her twin funnels removed, increasing the arc of fire for her anti-aircraft guns.

Alcantara was sent to Malta for further modifications, but en route she had a major collision with the Cunard ship RMS Franconia (1922). As a result Alcantara continued to Alexandria for hull repairs.

On 28 July 1940 Alcantara encountered the German GERMAN AUXILIARY CRUISER Thor in the South Atlantic. Thor scored three hits on Alcantara, and was hit twice by Alcantara's six-inch main guns. One of the hits on Alcantara flooded her engine room and forced her to reduce speed, allowing Thor to escape.

In 1943 Alcantara was converted into a troop ship.

Final years
Alcantara remained a troop ship well after the end of the war, and did not return to civilian service until October 1948. Asturias remained in UK Government service as an emigrant ship, and Alcantara alone resumed their route between Southampton and South America. In April 1958 she was withdrawn from service and sold to Japanese shipbreakers who renamed her Kaisho Maru, took her to Japan and broke her up in the same year.