Times of London duped by Bill de Blasio 'imposter' critical of Mamdani

A Times of London story which supposedly quoted former New York mayor Bill de Blasio criticising the Democratic candidate for mayor, Zohran Mamdani, was deleted after it emerged that de Blasio had never made those comments. The British newspaper then blamed the error on their journalist being duped by "an individual falsely claiming to be the former New York mayor". So who is the de Blasio imposter and how did The Times end up publishing this fake news story?