[4] They were intended to be towed through minefields that used pressure mines, creating a pressure wave that would detonate the mines; the open lattice construction of the ships would, according to the design, allow the blast to pass through the vessel without causing damage to it.

[4] The ships were constructed under conditions of the utmost secrecy;[5] they were originally referred to as 'Sterling craft',[4] then later designated as being part of the Algerine class of fleet minesweepers;[6] their design was still classified as late as the late 1960s.

[1] Both ships were launched in January 1944; transferred to Scott Lithgow, located on the lower Clyde, for completion and fitting out, the two vessels were commissioned in May of that year.

[1] Both ships of the class saw use during Operation Overlord, the D-Day invasion of northern France; although the two vessels proved successful in operational service, when damaged they were difficult to control, being "as difficult to handle as a battleship".

[8] Cyrus was wrecked in the Seine Estuary in December 1944;[8] Cybele survived the war, being scrapped in October 1946.