m is 0, 1, 2 or 3;

n is 0, 1 or 2;

t is 1 or 2;

A represents a phenyl ring optionally bearing up to 2 additional substituents selected from halogen, CN, CF₃, OR⁸, CO₂R^a, CONR^aR^b, NR^aR^b and C_1-4alkyl which is optionally substituted with halogen, CN, CF₃, OR^a, CO₂R^a, CONR^aR^b or NR^aR^b;

W represents —CR³═CR⁵, where R³ and R⁵ are selected from H, OH and F but mot more than one of R³ and R⁵ is other than H;

E represents a chemical bond or a straight or branched alkylene chain containing from 1 to 4 carbon atoms, optionally incorporating an oxygen atom to form an ether linkage and optionally comprising a hydroxy substituent;

Z is selected from H, halogen, CN, nitro, CF₃, OCF₃, —R^a, —OR^a, —SR^a, —SOR^a, —SO₂R^a, —SO₂NR^aR^b, —NR^aR^b, —NR^aCOR^b, —NR^aCO₂R^b, —NR^aCONR^aR^b, NR^aSOR^b, NR^aSO₂R^b, CONHCOR^a, NHCH₂CO₂R^a, NHCH₂CONR^aR^b, —NR^aSO₂NR^aR^b, —COR^a, —CO₂R^a, —CONR^aR^b, —CH═NOR^a or a five- or six-membered heteroaromatic ring optionally bearing up to 2 substituents selected from halogen, CN, CF₃, C_1-6alkyl, C_1-6alkoxy, C_1-6alkylthio, amino, C_1-6alkylamino and di(C_1-6)alkylamino;

or the moiety -E-Z may combine with an adjacent R² group as defined below;

R^a and R^b independently represent H or a hydrocarbon group of up to 7 carbon atoms which is optionally substituted with up to 3 halogen atoms or with CN, OH, C_1-4alkoxy, C_1-4alkylthio, amino, C_1-4alkylamino or di(C_1-4)alkylamino; or R^a and R^b, when linked through a nitrogen atom, together represent a heterocyclic ring of 4, 5 or 6 members, optionally bearing up to 3 substituents selected from halogen, CN, CF₃, oxo, OH, C_1-4alkyl and C_1-4alkoxy;

each R¹ independently represents halogen, CN, CF₃, OCF₃, C_1-6 alkyl, OH, benzylthio, C_1-6 alkoxy or hydroxymethyl; and

each R² independently represents halogen, CN, CONH₂, C_1-4alkyl or C_1-4alkoxy; or an R² group and the moiety -E-Z when attached to adjacent ring positions may complete a fused 5- or 6-membered carbocyclic or heterocyclic ring optionally bearing up to 3 substituents selected from halogen, CN, CF₃, oxo, R^a and amino; with the proviso that when A represents the residue of a phenyl ring and W represents —CH═CH—, m is not zero and at least one R¹ represents F;