Passivhaus EnerPHit Pre-Certification has been achieved following the completion of Phase 1 of this deep retrofit of a classic Victorian terraced house in London. Originally built around 1870, this three-bedroom home is being transformed to EnerPHit standards through a two-phase approach. Phase 1 included external wall insulation, high-performance windows, and the installation of whole-house mechanical ventilation with heat recovery (MVHR). Cayford modelled the building using the Passive House Planning Package (PHPP), and Pre-Certification confirms anticipated final energy savings of 96% compared to the original condition—achieving a space heat demand of just 13 kWh/m².yr. Phase 2 will include a full ground floor renovation, rear extension, and the integration of an air source heat pump. This project demonstrates the remarkable potential for decarbonising typical Victorian housing stock and stands among the most energy-efficient residential retrofits in the UK.