In case I've missed something- 40a mcb in an old Simplex cu feeding a standalone, plastic cu consisting of a 63a, 30ma rcd as main switch and a 40a mcb. 10mm t&e serving a 9.5 kw Mira shower via a 45a dp switch. Random tripping of the rcd when the shower is off ( power to the switch internal to the shower, but shower not running). Rcd ramps at 22ma, x1 & x5 results fine, Zs what you would expect with measured Zdb and length of cable. Insulation resistance 999 on all combinations and resistance of heating tank fine. All connections tight. Cable run in loft is visible, no damage. I wasn't able to ir test N-E on remaing circuits due to not being able to isolate on this first visit (am going back when house is unoccupied) but any thoughts meantime??