Reactive disazo dyes

A dye of the formula (I)

• wherein:
• each R, independently, is RA or RB,
• where RA is a group
• in which each of R1, R2, R3 and R4, independently, is a hydrogen atom or a C1-4 alkyl group;
• RB is a group
• in which:
• R5 is a hydrogen atom or an optionally substituted C1-4 alkyl group or an optionally substituted phenyl or naphthyl group;
• R6 is a hydrogen atom or an optionally substituted C1-4 alkyl group or an optionally substituted phenyl or naphthyl group or is a group NR5R7;
• where R5 is as defined above;
• and
• R7 is a hydrogen atom or an optionally substituted C1-4 alkyl group or is a group of the formula:
• COR5 or CO2R5
• where R5 is as defined above, or
• R5 and R6, together with the nitrogen atom to which they are attached, form a ring;
• at least one R is a group RA;
• when each R is RA, each RA may be the same as or different from the other;
• each Y, independently, is a labile atom or group;
• each of m, n and p, independently is zero, 1 or 2;
• SO3M is a sulphonic acid group or salt thereof;
• and
• each ring A and B, independently, is additionally optionally substituted.