The invention relates to certain pyrrolobenzodiazepines (PBDs), and in particular pyrrolobenzodiazepine dimers bearing C2 substitutions, including compounds of formula (T): wherein: R2 is CHR2A, and R2A is independently selected from H, R, CO2R, COR, CHO, CO2H, and halo; R6 and R9 are independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR′, NO2, Me3Sn and halo; R7 is independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR′, NO2, Me3Sn and halo; R8 is independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR′, NO2, Me3Sn and halo; R is independently selected from optionally substituted C1-12 alkyl, C3-20 heterocyclyl and C5-20 aryl groups; or the compound is a dimer with each monomer being of formula (M), where the R7 groups or R8 groups of each monomer form together a dimer bridge having the formula —X—R″—X— linking the monomers; wherein R″ is a C3-12 alkylene group, which chain may be interrupted by one or more heteroatoms, e.g. O, S, N(H), and/or aromatic rings, e.g. benzene or pyridine; and each X is independently selected from O, S, or N(H); or any pair of adjacent groups from R6 to R9 together form a group —O—(CH2)p—O—, where p is 1 or 2, and salts and solvates thereof, and their use as intermediates for the preparation of other PBD compounds.