The easy route south from Belstone through Birchy Lake onto Taw Marsh crosses the ruined dry stone wall called Irishman's Wall. This is an obvious feature and runs almost east-west, just south of Belstone Tor.
Crossing says he was reliably informed by a local source that this wall was an attempt to enclose a part of the moor, no doubt for the purposes of securing grazing and possibly mining rights for the landowner from the "commoners". Possibly it was also intended to block and/or control access into the central parts of the moor for such purposes, plus the economically important route for hauling quarried granite out towards Okehampton.
Crossing describes the wall as running west from the Taw as far as the Black-a-ven, where it turns south until it almost reaches the latter's headwaters, where it turns almost east and again strikes the Taw in Steeperton Gorge, just north of Knack Mine Ford.
The Belstone westward section of the wall is obvious, and the Steeperton eastward leg is clearly a ruined wall line. I have not explored up the banks of the Black-a-ven but sections of a wall line alongside the brook are shown on various OS maps.
Apart from forming an enclosure of the rectangular type described, a "newtake" as its called on the moor, its hard to see a reason behind the labour in building this wall. I'm not one to say Crossing was wrong, but what we have now is not one continuous wall but dismembered sections of ruined wall. I like to think its all one structure, but today this is conjecture based on reported hearsay.