A group of four gold rings

A group of four gold rings, comprising: an 18ct gold ring set with five graduated circular-cut diamonds, size L, stamped 18ct, maker's mark CS FS; two smaller five-stone diamond rings mounted in 18ct gold, sizes K and L, one with diamond deficient and British hallmarks, the other stamped 18; and an 18ct gold ring set with three circular-cut sapphires spaced by rose-cut diamonds, size O, British hallmarks