She was built by Scotts Shipbuilding and Engineering Company (Greenock, Scotland), with the keel being laid down on 19 April 1939.

Known as the 'toothless terrors', they proved to be very good anti-aircraft ships, often leading to comparisons with their sisters armed with the heavier QF 5.25 in (133 mm) guns.

In February she returned to the Home Fleet for Arctic convoys but was back in the Bay of Biscay by June 1943 to cover anti-submarine operations.

There was a pleasant reunion, then Mary B Mitchell resumed her voyage to Lisbon, and Scylla continued her search for blockade runners.

Scylla was the allotted RN flagship for the Normandy landings and the flagship for Vice Admiral Philip Vian and it was considered vital to all shipping and naval movements in the area, particularly that of coastal RN MTBs and enemy E boats, to prevent blue on blue incidents.