Flag of the Civil Defence Service, first flown in 1943. Some (possibly locally-manufactured) variants exist in 2:1 ratio and lacking the lettering and crown.
Source: Own work, incorporating some public-domain images, and based on an image at <a rel="nofollow" class="external free" href="http://www.crwflags.com/fotw/flags/gb_cd.html">http://www.crwflags.com/fotw/flags/gb_cd.html</a>
<a href="https://en.wikipedia.org/wiki/User:Wally_Wiglet" class="extiw" title="wikipedia:User:Wally Wiglet">Wally Wiglet</a> at <a href="https://en.wikipedia.org/wiki/" class="extiw" title="wikipedia:">English Wikipedia</a>
9 November 2010 (original upload date)
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