Bit stuck here!

[Goody]

Been to a flat to test prior to changing the consumer unit. Two rings and two light circuits but none of them has an earth cable, just phase and neutral but Zs at the sockets are good. It’s a TNS system with Ze of 0.26 ohms. How do I go about finding R1+R2 for the rings in this situation? Thanks!

 

[telectrix]

is it wired in steel conduit, using the conduit as cpc?

 

[Goody]

Yes, I can see some section but not that visible under the metal boxes embedded in the wall. I am sure, the steel conduit should be responsible for such a nice Zs values.