David Calling  The David Pryce-Jones blog.  Another Day . . .
Another day, another Soviet spy revealed in the heart of the
British establishment. The spy this time is James MacGibbon, who
in the war worked in a special department of the War Office and
passed documents to his Soviet handler in London. A Russian
historian, Svetlana Chervonnaya, has been exploring the relevant
files. At the same time, MacGibbon’s son, Hamish, has published
an article in the London Review of Books, a left magazine that
rejoices in anything harmful to Britain.  This article explains
how James MacGibbon had been a member of the Communist party
before the war but still passed the War Office vetting, like so
many other dubious figures. German intelligence had penetrated
parts of the Soviet secret service, and MacGibbbon could have
given away information that exposed Ultra, the code name for
British interception of German radio traffic unknown to the
Germans. In that case, as Ben Macintyre, a specialist in these
matters, points out