Abstract: The present invention describes an image dye-forming coupler of formula (I) ##STR1## wherein L is an oxymethylene or oxycarbonyl group; n is 0 or 1; COUP is a coupler moiety and R.sub.1 and R.sub.2 are the same or different and are groups selected such that(a) together with the nitrogen atom a good leaving group is formed;(b) at least one of them contains a PUG linked to an electrophilic center (E); and(c) neither R.sub.1 nor R.sub.2 is a hydrogen atom wherein the coupler is a DIAR coupler from which inhibitor is released from a coupling-off group after a timed delay which results from an additional reaction step. Such delay permits control over the time of release, rate of release and rate of diffusion of a photographically useful group (PUG) without altering the nature of the PUG itself.A method of preparing the coupler is also described wherein the two parts of the molecule can be built up separately and combined in a single reaction allowing ready access to a large variety of possible structures.