A steel cord (200) is described that is simple and cost effective to produce while solving some particular problems for the reinforcement of elastomer belts such as timing belts or the like. The cord (200) is a single lay cord that comprises a core filament (202), around which a first layer and a second layer of filaments (204, 210, 212) is twisted, all filaments being twisted with the same lay length and direction. By appropriate choice of the lay length, the core filament diameter and the filament diameters of the first layer—the latter being larger or equal to the former—an aggregate gap can form in which intermittently a filament (210′) of the second layer gets entrained. This aggregate gap must be between 40 and 70% of the core filament diameter in order to obtain the desired effect of having a core filament (202) that is deformed with the same lay length and direction as the other filaments (204,210,212). A deformed core filament (202) suppresses the effect of core filament migration. In addition the exceptional rough aspect of the cord (200) leads to good mechanical anchorage in the elastomer. Also the load exerted on the cord (200) is better distributed over all filaments. The use of the cord is not limited to timing belts: an advantageous use of the cord in tyres, hoses, hoisting belts, drive belts and reinforcing strips is anticipated.