BT use an instrument which is basically an oscilloscope and a
pulse generator. The pulse goes down the cable and bounces back
from where the break is. The initial pulse followed by the
'echo' are displayed on the 'scope, from which can be determined
the time between the two and thus the distance to the fault.

Probably does not help with where the cable is located - though
you could do the same for both ends, add the two lengths
together and it would give the limits of where it could be.


Suggest a metal detector would help you plot the cable route.

What Harry described is a Time-Domain Reflectometer (aka TDR). Not
a lot of people know that.

Not a lot know how expensive they are either. We use one for finding
faults on co-ax cables up transmission towers.....
--
Tony Sayer