[Ru(phen)2(tpphz)]2+ (tpphz = tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]phenazine), Ru1 (Fig. 1a), is a water-soluble hydrophilic mono-intercalator (log P = –1.24, DNA Kb = 3 × 105 M–1) that shows in vitro anti-cancer activity31 and toxicity has been established in murine models.32 Here, we present a detailed characterisation of the cellular response to DNA damage generated by Ru1 in p53-deficient oesophageal cancer cells and explore the complex in combination with IR. Here, SFMBT1 is linked to cancer.