Part of the WW2 anti-invasion defences that formed part of Western Command Stop Line No.21, which ran from Rhyl to Machynlleth. The whole structure measures approximately 72m long N-S and is bisected by the A470. Ten anti-tank blocks made of local dressed stone are on the S side of the A470. (15 blocks on the N side of the road are recorded separately [nprn 270351]). The 10 blocks on the S side of the road are 1.5m square and 1.4 - 1.7m high, depending on the slope of the ground, and are of mortared rubble stone. A stream passes through at the lower end (S), causing some erosion, whilst the gaps between the blocks have been infilled with dry rubble.

Recorded as part of RCAHMW Uplands Initiative Project, W B Horton, H&H, 25/09/2012.

Surviving Anti-invasion defences (anti-tank cubes) around Fairbourne and Cader Idris: part of Western Command Stop Line No.21

• 270354 Fairbourne Anti-invasion defences (scheduled)
• 800145 Anti-invasion defences, Arthog
• 800146 Anti-invasion defences Llyn Gwernan
• 414156, Anti-invasion defences, Dysyrnant, Happy Valley/Cwm Maethlon
• 270352 Anti-invasion defences, Bwlch Llyn Bach/Cwm Rhwyddfor (scheduled)
• 270350/270351 Anti-invasion defences, Bwlch Oerddrws, east of Cae’r tyddyn (scheduled)

T. Driver, Royal Commission, 26 July 2023