I did a loop impedance test today at a garage socket with ATT on and got a measurement of about 250Ω, I did it again without ATT and measured about 2.5Ω. I have noticed small discrepancies before, but never on this scale. I did repeat the tests, and am fairly sure I was reading the display properly! The house is PME, presumable exported to the garage. I didn’t have time to investigate further, and am going back on Monday so can look into it further then. I am wondering what could cause such discrepancies. My meter has fairly new batteries in it.