Though out of place for 'Plotii', the Hertfordshire plot-like elms may be the same population noted by Druce yet ignored by Melville. Whilst they may not necessarily be genetically identical to the trees at Caythorpe or Laxton, they may well represent a very similar clone.
Tree in centre
Tree to right of centre
Tall tree to right hand side.
Tree to right of centre
Image take from: http://oreald.com/picture1112.html