Further volumes, published after the privatisation of HMSO or in the series about the Special Operations Executive, are also useful.
The volumes were intended to be read individually, rather than in series, which led to some overlapping.
In their introductions to their parts of the series, Sir Keith Hancock and Sir James Butler wrote that this was to obviate a need to read more volumes than those covering that part of the war effort.
A parallel series of volumes for official use were printed, which referenced the unpublished sources in manuscript, in red ink[citation needed].
[citation needed] A number of official histories were produced by government departments.