This is the poster produced by the Navy League in 1913 as a key part of its campaign to force the government to increase the amount it spent on military and naval aviation -- or as the poster itself puts it, rather more succinctly:
THE NAVY LEAGUE
Describing this poster as a holy grail is somewhat of an overstatement, but it had been proving elusive. I'd read a description of it in the popular press, and found some information about where it was distributed and how much it cost in the Navy League archives, but I hadn't managed to find an actual reproduction of it until I looked at The Navy, May 1913, 135. The official organ of the Navy League was always a likely bet, but when I visited the UK last year, the British Library's copies were unavailable due to the move from Colindale to Boston Spa, and the relevant volume in the Navy League archives was missing. So, naturally, I found a copy in the State Library of Victoria on a quick visit during my holidays.
The description I'd already had turns out to have been perfectly accurate, and so arguably being able to see the design rather than read about it adds little (though the lines of airships and aeroplanes rising up behind Britannia might suggest it an influence from the Illustrated London News). But it will make a nice illustration for an article -- and even nicer if I can find a colour version...