[2][3] She was laid down at Swan Hunter's Wallsend shipyard on 21 May 1929, was launched without ceremony on 12 February 1930 and completed on 25 June that year.

The turbines developed a total of 2,000 shaft horsepower (1,500 kW) and were designed to give a maximum speed of 16.5 knots (30.6 km/h; 19.0 mph).

Folkestone stood by the stranded ship while salvage attempts were made, but these were prevented by the heavy seas and Antung was wrecked, with about 50 passengers and crew missing.

The outbreak of the Second World War led to this conversion being abandoned, however, and after being partially rearmed, she was ordered back to British waters where she arrived in February 1940.

[13][15] On 17 October 1940 off Iceland, Folkestone rescued seven survivors from SS Doka, a Norwegian merchantman sunk by the German submarine U-93.

[13] Folkestone was refitted again at Cardiff from April–June 1942, being fitted with Centimetric Type 271 radar and a Hedgehog anti-submarine mortar.

Folkestone detected radio signals from a German submarine with the ship's High-frequency direction finding gear, and running down the bearing found U-333, and carried out a series of six depth-charge attacks on the submarine, which was badly damaged, with its starboard propeller shaft bent upwards, and forced to abort its patrol.

[20][21] Folkestone was refitted at Grimsby in April–May 1943 before joining the Western African Command, operating out of Freetown on convoy escort duties.

She returned to England in September 1943 for a refit at Liverpool, during which she suffered a minor boiler explosion on 13 November.

[13] In September 1944 Folkestone returned to Britain, and after a survey indicated that she was beyond economic repair was laid up at Milford Haven.