the dashed line joining A and C(R^a) is present and represents a bond and A is a —C(R^b)═ group;

R^a and R^b are each hydrogen;

X is a —CH═ group;

Y is a —C(R^e)═ group;

R^e is hydrogen, —CN, —COR¹, —CO₂R¹, —CONR^1aR^2a, —S(O)₂NR^1aR^2a, —CONR^1a OR^2a or —C(O)N(R^3a)NR^1aR^2a;

R¹ is methyl, ethyl or trifluoromethyl

R^1a and R^2a are, independently, a hydrogen atom or methyl group, or together with the nitrogen atom to which they are attached, represent —(CH₂)₄— or —CH(CH₂OH)(CH₂)₃—;

R^3a is a hydrogen atom or C_1-6alkyl group;

L is a —CH₂—, —CH(CH₃)—, —C(O)— or —CH₂CH₂— group;

n is zero;

Alk¹ is an optionally substituted aliphatic or heteroaliphatic chain;

L¹ is a covalent bond;

Cy¹ is phenyl, methylphenyl, methoxyphenyl, thienyl or indolyl; and

Ar represents phenyl, pyridinyl, thienyl or benzothienyl, any of which groups may be optionally substituted by one or two substituents selected from halogen, cyano, C_1-6 alkyl, C_1-6 alkoxy and nitro;