Hexanuclear thiolato-bridged arene ruthenium metalla-prisms of the general formula [(p-cymene)6Ru6(SR)6(tpt)2]6+ (R=CH2Ph, CH2C6H4-p-tBu, CH2CH2Ph; tpt=2,4,6-tris(4-pyridyl)-1,3,5-triazine), obtained from the dinuclear precursors [(p-cymene)2Ru2(SR)2Cl2], AgCF3SO3 and tpt, have been isolated and fully characterised as triflate salts. The metalla-prisms are highly cytotoxic against human ovarian cancer cells, especially towards the cisplatin-resistant cell line A2780cisR (IC50 <0.25M).