Barrett’s oesophagus(BO)is a usually indolent condition that occasionally requires endoscopic therapy.Radiofrequency ablation(RFA)is an effective endoscopic treatment for high grade dysplasia(HGD)and intramucosal cancer in BO.It has a good efficacy,durability and safety profile although complications can occur.Here we describe a case of RFA in a patient with high grade dysplasia.Although the response to treatment was initially very good with the development of neosquamous epithelium,the patient very rapidly developed a squamous cell cancer of the oesophagus confirmed on radiology,histology and immunohistochemistry.Sanger sequencing confirmed that the original HGD and the squamous cell cancer(SCC)were derived from separate clonal origins.The report highlights the fact that SCC of the oesophagus has been noted after endoscopic ablation for BO previously and suggest that ablation of BO may encourage the clonal expansion of cells carrying carcinogenic mutations once a dominant clonal population has been eradicated. Barrett’s oesophagus (BO) is a usually indolent condition that occasionally requires endoscopic therapy. Radiofrequency ablation (RFA) is an effective endoscopic treatment for high grade dysplasia (HGD) and intramucosal cancer in BO. It has a good efficacy, durability and safety profile complications can occur. Here we describe a case of RFA in a patient with high grade dysplasia. Although the response to treatment was minimal very good with the development of neosquamous epithelium, the patient very developed a squamous cell cancer of the oesophagus confirmed on radiology , histology and immunohistochemistry. Stanger sequencing confirmed that the original HGD and the squamous cell cancer (SCC) were derived from separate clonal origins. The report highlights the fact that SCC of the oesophagus has been noted after endoscopic ablation for BO previously and suggest that ablation of BO may encourage the clonal expansion of cells carrying carcinogenic mutations once a dominant clonal pop ulation has been eradicated.