Four-number Trench Map Coordinates query

[jaykayu]

Hi

 

Can anyone help explain and identify the location of the four number map reference on the CWGC Grave Concentration form below please.?

 

The form is for Ham British Cemetery and in the column 4th from the left titled ''Approximate Map Reference where body found' you will see  a four number map reference for the original location of all 13 bodies, which is 66-58. You can also see underneath 'Approximate Map Reference where body found' at he top of this column the hand writing  'Ref Trench Map Ham 1:20,000.

 

Note the approx location coordinates of Ham British Cemetery is written separately in normal format in the 'Name of Cemetery of Re-burial' row, e.g. 66D.Q.2.a.1.4 so this can be easily located.

 

Any clues how I can get a 1:20,000 Trench map of Ham ( NLS/McMasters don't appear to have one) and how to apply the 4 number coordinates please? or any other clue to identify the location of these coordinates 66-58  please?  

 

FYI This use of varied 4 number coordinates is common on Grave Concentration forms for Ham cemetery, which specify they relate to a 1:20,000 trench map of Ham and elsewhere, e.g a 1:20,000 trench map of Nesle. 

 

Really appreciate any help, Thanks.

 

J