Compounds of formula (V) may also be prepared by reacting the corresponding imidazole of formula (VI) with a compound of formula (VIIIa) or (VIIIb) ##STR19## wherein R6 is as defined in formula (V) above and R7 and R8, which may be the same or different, may each represent suitable leaving groups for example halogen atoms (e.g. chlorine, bromine or iodine), acyloxy groups for example sulphonyloxy