caz
and a formation could contain more than one mark.
Well now, that solves a question I have had in the back of my mind for yonks! As a lad growing up in the Vale of York/Hambleton Hills many moons ago I would sometimes see some right old raggle taggle JP formation trundling past; that explains it. I did eventaully get a trip in the Linton wx ship one morning, very good. Fixed power, variable noise! Thanks
