The last of the movable mills to survive of those that existed in the Fens was at Parson Drove. Fortunately, well illustrated and photographed before it disappeared. In 1857 the mill was brought to its final site until it was demolished in 1914
When a new site was chosen for the mill, a circle was dug in the ground about 20' diam. and 3' deep; a track was laid down consisting of stones about 3' square and a pole was run up at the centre of the circle. Three horizontal poles were attached radially to the centre one, which acted as a pivot and at their outer ends were fixed three rollers, which ran round on the stone track, the poles being linked together so that the relative positions of the rollers to each other could not vary. All these parts were brought from the previous site. Turf blocks about 12" deep and cut obliquely were arranged herring-bone fashion to form a wall about 4' high and just over 28' diam. around the track, leaving a raised platform about 4' wide round the excavated circle. A conical thatched wooden roof completed the mill; turf, timber and thatch were renewed each time the mill was moved. The original rollers were of stone and would not climb the woad well, but later tapered rollers were introduced made with wooden hubs and iron bars, about forty in number. The first roller had the narrowest bars, the middle roller the medium and the last roller the widest bars When the mill was being worked, a horse was hitched to each roller pole, the direct pull to be given by the horse.
The thatched wing of the mill was used as a couching house and was stone-paved with a floor space of 50' by 20', and the walls were of turf. The opposite wing was constructed in a similar manner but had a boarded roof. The pens for storing the dried woad balls were open wooden structures with boarded roofs and were placed adjacent to the two wings the drying ranges ran behind the mill and stretched for some distance on either side.