In one embodiment, where any of R1 to R14 is directly substituted by an alkyl substituent group, or by an alkyl-containing substituent group (such as alkoxy or alkylcarbonylamino for example), then the alkyl moiety of the substituent group directly attached to any of R1 to R14 may be further substituted by the substituent groups hereinbefore described and particularly by halogen, hydroxy, alkoxy,