The property in question has a metered, plastic supply pipe, partially mdpe partially alkathene running up a shared tarmac drive to the front, then concrete border at the side of the property and a slabbed area at the rear. The leak was 180 litres per hour. Previous attempts by others to locate the leak acoustically had been unsuccessful so we were engaged to carry out gas insertion. There was previous knowledge of the pipe route from the meter to the point of entry into the house and this knowledge combined with the gas insertion technique enabled the leak to be located. The leak position was marked with chalk in readiness for others to repair.