Thought it was inrush at first but only a tv and couple of lamps plugged into the circuit at the moment. It held with nothing plugged in but couldn’t wait around all day as clients quite a pain!. It also holds with loads in and trips unannounced not when client turns something on etc which is usually the problem. Thanks for replyTwo reasons for the trip - either overload (/inrush) or earth leakage. A clamp meter will help with the first and a full IR test the other. You say it’s ‘quite long’ - that always makes me suspicious of a joint or other connection somewhere that you haven’t found yet. An R1R2 measurement will help you know exactly how long (look up the resistance values in the OSG and do the maths). Also, does the circuit hold with zero appliances connected? Again, that splits it down to either the installed circuit or a faulty device.