[rafcommands]

Hi Jens,

You are correct that Coastal Command and the Admiralty used the same codes. In general the letter groupings were changed every three months but sometimes more frequent.

I do not know how much you know about them but:

The codes are of the form XXYY aabb where

XX is the Lat Degree
YY is the Long Degree
aa is the Lat minute
bb is the Long Degree

I do not have the codes for April 1940 to hand until I get back home at the weekend but both are the same Lat Degree and Minute eg MB 55.

The codes are in the National Archives but hidden in an obscure location so I'm not surprised the staff could not guide you. I am producing a decoder 1939 to 1945 (53N to 62N) as an appendix for Vol 3 of RAF Coastal Command Losses.

I'll answer with more detail at the weekend.

Regards
Ross