Arkroyal
I never believed them to be sloppy - I referred to the tone of some of the comments in the inquiries; eg
1034. …Sir John. The point which you have marked, the Waypoint…….was the lighthouse 0.81 nautical miles away,…..?
(Sir John Day) I can remember the details, my Lord. The point that they had plotted as the lighthouse, which was actually incorrect, if you recall, so the computer, and presumably they, both thought that Waypoint Alpha was the position of the lighthouse, as it turns out, we now know that they had slightly misplotted it.
To me, someone should have pointed out the actual feature that was used.
Regards portable TACAN - you may find it interesting to look up "PRC-112" type equipments - to see how small they are, that they have the ability to be used as portable DMEs (only weigh 28 ounces) and the uses of them, particularly for marking isolated navigation hazards near landing zones in operational areas.
ZD576s IFF system was set to mode 3a which interrogates any such set in range - giving a very accurate range.
My big point now is that, there was no mention of this embedded (in the IFF system) navigation aid that was available to them (and the on board equipment set appropriately) in the inquiries - yet every other thing was thoroughly gone over.