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That is in fact a pseudonym used by Augustus the Younger, Duke of Brunswick-Lüneberg, who as well as this work on cryptography, had also written on chess.

Tables and illustrations of ciphers, codes and cryptograms illustrate the work but it was the titlepage that drew the attention of Sir Edwin Dunning- Lawrence, who saw in it pictorial puns that pointed to Bacon as the true author of the works we credit to Shakespeare and put forward his theories in a pamphlet of 1914.

One panel (centre left) is said to show Bacon handing a text to Shakespeare (the man holding a spear), while the panel at the foot of the page supposedly depicts Augustus holding the Cap of Maintenance over the head of Bacon as he writes.

Others dismiss such claims, but this first of the Selenus book, in an early calf binding, did sell for $6000 (£4800) in a PBA Galleries (20/15% buyer’s premium) sale of February 12 in Oakland, California.