Liverpool has become the latest flashpoint in Britain's simmering HMO debate, with residents and councillors in one part of the city warning that a loophole in planning and licensing rules is allowing houses in multiple occupation to proliferate unchecked. The phrase being used locally - a 'crack in the system' - is telling. It suggests not a single rogue landlord or a one-off enforcement failure, but a structural gap that savvy operators are exploiting at scale, converting family homes into shared housing faster than the council can track, let alone control, the change.