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. Fifteen anti-tank blocks made of local dressed stone are on the N side of the A470 (10 blocks on the S side of the road are recorded separately [nprn 270350]). The 15 anti-tank blocks, each 1.5 x 1.55m and 1.3-1.4m high, are of cement-mortared rubble stone. The line runs SSE-NNW from the A470 road, up to a bank. There are gaps 0.9m wide between the blocks, which have been infilled with dry rubble stone.

Recorded as part of RCAHMW Uplands Initiative Project, W B Horton, H&H, 02/10/2012.

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