The phase behaviour of mixtures of the liquid crystalline compound 4-cyano-4’-n-pentylbiphenyl and the photoactive chromophore methyl beta-(1-naphthyl)propenoate is reported. Incorporation of the chromophore into the liquid crystal host leads to depressions of the nematic-isotropic transition temperature of up to 12 degrees C. Further photo-induced depressions of the nematic-isotropic transition temperatures of up to 4 degrees C are recorded. These photo-induced shifts result from the optically pumped geometric E double right arrow Z isomerisation of the chromophore to largely the Z isomer. Both isomers of the chromophore are non-mesogenic and the results demonstrate the wider range of chromophores, which undergo geometric isomerisation, that can be utilised for these light activated structural changes including isothermal photo-induced phase transitions.