Paul Bettany plays Doctor Stephen Maturin in the film Master and Commander. Courtesy of 20th Century Fox.
If you have only seen the film of Master and Commander: The Far Side of the World you will not be aware that Dr Stephen Maturin is one of the Admiralty's most prized intelligence agents.
Although O'Brian hints at it in the first book of the series, this is not made apparent to readers until the second volume. Thereafter he gives the impression that there is an organised structure of spies working for the Admiralty. This is, of course, fiction.
There was no such thing. Although Nelson's chaplain, Dr Alexander James Scott, may have been involved in some espionage, subterfuge and secret negotiations, there was no network, no spymaster and no Georgian version of "M".
The nearest thing to MI6 was the Secret Office, three rooms adjoining the Foreign Office, but with a non-descript entrance in Abchurch Lane, in the City of London.
MI6 HQ - Today Britain's foreign espionage services operate from this suitably monolithic building at Millbank.
Historians say that no more than 30 people ever knew of its existence. Its role was to intercept, with the help of the Post Office, foreign correspondence. A staff of 10 included experts at breaking seals and forging new seals on diplomatic letters.
Correspondence written in code, was sent by personal courier, to the grandly named Deciphering Branch of the Department of the Secretary of State. In reality, this was a family business begun in the 18th century by the Rev. Edward Willes and then taken over by two of his sons and three of their nephews.
They cracked coded messages and devised new ones. They were well rewarded and became an extremely wealthy family.
Max Glaskin is an award-winning freelance journalist regularly published in the Sunday Times, New Scientist and many other national publications.