A herbicidal compound of formula (I) :
or N-oxide or quaternised derivative thereof;

in which the dotted lines indicate the presence of two double bonds arranged so as to form a fused hetero-aromatic ring system;
Ar is an optionally substituted aryl or heterocyclic ring system;
W is 0 or NR 1
where R 1 is H or lower alkyl;
A, B, D are independently selected from N, NR 2 , N-E, CR 6 , C-E or C(R 6 )E;
wherein E is:
provided 2 of A, B and D are N, NR 2 or N-E and at least one of A, B or D carries a group E;
where R 2 is H, OR 7 , CN, COOR 8 , alkyl or haloalkyl;
R 3 and R 4 are independently selected from H, optionally substituted alkyl, alkenyl or alkynyl, halogen, NR 9 R 10 , or
R 3 and R 4 together with the carbon to which they are attached form an optionally substituted alkenyl or cycloalkyl group;
R 5 is CO 2 R 11 , CN, COR 11 , CH 2 OR 11 , CH(OH)R", CH(OR 11 )R 12 , CSNH 2 , COSR 11 , CSOR", CONHSO 2 R 11 , CONR 13 R 14 , CONHNR 13 R 14 , CONHN + R 13 R 14 R 15 Y-, CO 2 -M + or COON=CR 13 R 14 ;
X is (CH 2 ) n , CH=CH, CH(OR 16 )CH 2 or COCH z ;
where n is 0, 1 or 2;
M is an agriculturally acceptable cation;
Y- is an agriculturally acceptable anion;
R 6 is H, halogen, OR 7 , CN, COOR 8 , alkyl or haloalkyl;
R 7 and R 8 are independently H or lower alkyl;
R 11 , R 12 and R 16 are independently selected from H or an optionally substituted alkyl, alkenyl, alkynyl or aryl group; and
R 9 , R 10 , R 13 , R 14 and R 15 are independently selected from H or an optionally substituted alkyl, alkenyl, alkynyl or aryl group or any two of R 9 , R 10 , R 13 , R 14 and R 15 together with the atom to which they are attached form a cycloalkyl or heterocyclic ring providing that the compound is other than 5-(2,4-dichlorophenoxy)indazol-1- ylacetic acid or its methyl ester.

Process for the preparation of these compounds and compositions containing them are also described.