A compound with the formula (I), wherein: R2 is of formula (II), where X is selected from the group comprising: OH, SH, CO2H, COH, N=C=O, NHNH2, CONHNH2, formula (A), formula (B), NHRN, wherein RN is selected from the group comprising H and C1-4 alkyl RC1, RC2 and RC3 are independently selected from H and unsubstituted C1-2 alkyl and either: R12 is selected from the group consisting of: (ia) C5-10 aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, C1-7 alkyl, C3-7 heterocyclyl and bis-oxy-C1-3 alkylene (ib) C1-5 saturated aliphatic alkyl (ic) C3-6 saturated cycloalkyl (id) formula (C), wherein each of R21, R22 and R23 are independently selected from H, C1-3 saturated alkyl, C2-3 alkenyl, C2-3 alkynyl and cyclopropyl, where the total number of carbon atoms in the R12 group is no more than 5 (ie) formula (D), wherein one of R25a and R25b is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy pyridyl and thiophenyl and (if) formula (E), where R24 is selected from: H C1-3 saturated alkyl C2-3 alkenyl C2-3 alkynyl cyclopropyl phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy pyridyl and thiophenyl R6 and R9 are independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR, nitro, Me3Sn and halo where R and R are independently selected from optionally substituted C1-12 alkyl, C3-20 heterocyclyl and C5-20 aryl groups R7 is selected from H, R, OH, OR, SH, SR, NH2, NHR, NHRR, nitro, Me3Sn and halo either: (a) R10 is H, and R11 is OH, ORA, where RA is C1-4 alkyl (b) R10 and R11 form a nitrogen-carbon double bond between the nitrogen and carbon atoms to which they are bound or (c) R10 is H and R11 is SOzM, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation R" is a C3-12 alkylene group, which chain may be interrupted by one or more heteroatoms, and/or aromatic
