Monument record MRM 149 - HFDF (High Frequency Direction Finder) tower, Adastral Park, Martlesham

Whilst this structure is similar in size and shape to a Type 27 pillbox and also fits the typical description, being ‘usually found on or near airfields … with an open central well’ its walls are not the usual 0.9m (3ft) thick (Lowry, 1995). It also does not appear to have had a roof, which is normally present on the outer area, forming a ring shape around the central well to protect those firing from the loopholes. The previous building record stated that the structure was actually used as a protective skirting around the base of a HFDF (High Frequency Direction Finder) tower, for which the internal octagonal concrete and iron rods formed the foundation. However, no sources were provided to confirm this conclusion and no further information has been found to verify this (S2).