There is yet another reference to Boar Castle in 1841. Track it via William SPENCER, 30, Ag Lab, not born in county.

Well spotted Mike ! AND it's within the Parish of Llangarron, too, which fits.
Still cannot find it on any maps tho...

Thanks Sid for checking the transcript re "Farm Bailey" - hope you can understand why I thought it might have been "bailiff", ah well...

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