This is in an area where the drainage ditches form part of a larger scheme. The ditches on the parish boundaries serve both sides of the boundary. Are they in some way treated as common land to the two parishes? Chris H.
Um, The OS website does seem to have been revised to make this diagram more difficult (or impossible) to find. An index to the 1:50,000 Landranger maps is provided by the Charles Close Society at http://www.charlesclosesociety.org/files/GB_50.pdf but the link to this seems to have dropped off our index page! (John, please note) Chris H.
Could the symbol be intended to refer to Park Royal rather than Twyford Abbey? Probably a red herring, but there are several online references to munitions factories in the Park Royal area, but I haven't been able to find exact locations. Chris H.
Apologies for the circulation of the message apparently from Hugh Brookes with the subject 'Important'. Do not click on the link in this message, it is very likely to contain a virus. This looks like a currently prevalent form of hacking attack and I am sure that Hugh, himself, was unaware of the message being sent. Chris H.