(not very likely though. most houses are festooned with supplementary bonding and parallel earth paths)
There is earthing that goes to every pipe under the boiler that the original sparky installed along with a 10mm earth going back to the CU unit
I would guess that the rcd would of tripped if there was a issue?
If the sparky turns up with a clamp meter just test it and discuss it later.
It may be clean or it may not be. if it isn't it will solve your problem.