Question: About which famous battle did the author of the book Sea Lord write a nonfiction book ? 

Context paragraphs:
Francis Bridgeman (Royal Navy officer): Admiral Sir Francis Charles Bridgeman Bridgeman (7 December 1848 – 17 February 1929) was a Royal Navy officer.  As a captain he commanded a battleship and then an armoured cruiser and then, after serving as second-in-command of three different fleets, he twice undertook tours as Commander-in-Chief of the Home Fleet with a stint as Second Sea Lord in between those tours.  He became First Sea Lord in November 1911 but clashed with First Lord of the Admiralty Winston Churchill on technical issues as well as matters relating to a perceived overriding of naval traditions by Churchill: this led to Bridgeman's resignation just a year later.

The Lord of the Rings: A Reader's Companion: The Lord of the Rings: A Reader's Companion (2005) is a nonfiction book written by scholars Wayne G. Hammond and Christina Scull.  It is an annotated reference to J. R. R. Tolkien's "The Lord of the Rings".  Hammond and Scull proceed chapter-by-chapter from the original foreword through to the end of "The Lord of the Rings".  Appendices, examining the evolution of the text, changes, inconsistencies, and errors, often using comments from Tolkien's own notes and letters.  Other sections cover the numerous maps of Middle-earth, chronologies of the story and its writing, and notes on the book and jacket design of the first editions of 1954-55.  The book includes some previously unpublished material by Tolkien.  It also reprints part of a 1951 letter in which Tolkien explicates, at some length, his conception and vision of "The Lord of the Rings".  Reprinted for the first time since 1980, and corrected and expanded, is Tolkien's "Nomenclature of The Lord of the Rings" (previously referred to as "Guide to the Names in The Lord of the Rings"), an index of persons, places, and things designed to aid the translator in rendering Tolkien's work into foreign languages.  It is available in both hardcover and paperback.

Sea Lord (novel): Sea Lord (a.k.a. Killer's Wake in the United States) is a 1989 thriller novel by the British author Bernard Cornwell, one of a series of sailing-based thrillers.  It was published by the Penguin Group.

Jonathon Band: Admiral Sir Jonathon Band {'1': ", '2': ", '3': ", '4': "} (born 2 February 1950) was the First Sea Lord and Chief of the Naval Staff from 2006 to 2009, the most senior serving officer in the Royal Navy.  Before serving as First Sea Lord he was Commander-in-Chief Fleet.  Since becoming First Sea Lord, Band had been a firm advocate of the creation of new ships to meet new threats and maintain the status of the Royal Navy as one of the world's leading naval forces.

First Sea Lord: The First Sea Lord and Chief of Naval Staff (1SL/CNS) is the professional head of the United Kingdom's Royal Navy and the whole Naval Service.  Originally the title was the Senior Naval Lord to the Board of Admiralty when the post was created in 1689.  The office holder was then re-styled First Naval Lord from 1771.  The concept of a professional "First Naval Lord" was introduced in 1805 and the title of the First Naval Lord was changed to "First Sea Lord" on the appointment of Sir Jackie Fisher in 1904.  From 1923 onward, the First Sea Lord was a member of the Chiefs of Staff Committee; he now sits on the Defence Council and the Admiralty Board.

Elyssa East: Elyssa East is an American nonfiction writer.  She is the author of the creative nonfiction book "Dogtown: Death and Enchantment in a New England Ghost Town", which chronicles a murder that occurred in an area known as Dogtown, Massachusetts, just outside Gloucester, in 1984.  As part of her research for the book, East interviewed the murderer, Peter Hodgkins, in prison.  This nonfiction book won the 2010 L. L. Winship/P. E.N. New England Award and has been critically reviewed.  According to East, the book was inspired in part by the paintings of Dogtown by Marsden Hartley.

The Spanish Frontier in North America: The Spanish Frontier in North America is a nonfiction book written by historian David J. Weber.  The Texas Institute of Letters named it the best nonfiction book of 1992.  The Spanish Ministry of Culture also recognized it.

David Beatty, 1st Earl Beatty: Admiral of the Fleet David Richard Beatty, 1st Earl Beatty (17 January 1871 – 11 March 1936) was a Royal Navy officer.  After serving in the Mahdist War and then the response to the Boxer Rebellion, he commanded the 1st Battlecruiser Squadron at the Battle of Jutland in 1916, a tactically indecisive engagement after which his aggressive approach was contrasted with the caution of his commander Admiral Sir John Jellicoe.  He is remembered for his comment at Jutland that "There seems to be something wrong with our bloody ships today", after two of his ships exploded.  Later in the war he succeeded Jellicoe as Commander in Chief of the Grand Fleet, in which capacity he received the surrender of the German High Seas Fleet at the end of the war.  He then followed Jellicoe's path a second time, serving as First Sea Lord—a position that Beatty held longer (7 years 9 months) than any other First Sea Lord in history.  While First Sea Lord, he was involved in negotiating the Washington Naval Treaty of 1922 in which it was agreed that the United States, Britain and Japan should set their navies in a ratio of 5:5:3, with France and Italy maintaining smaller ratio fleets of 1.75 each.

Bernard Cornwell: Bernard Cornwell, OBE (born 23 February 1944) is an English author of historical novels and a history of the Waterloo Campaign.  He is best known for his novels about Napoleonic Wars rifleman Richard Sharpe.  Cornwell has written historical novels primarily of English history in five series and one series of contemporary thriller novels.  A feature of his historical novels is an end note on how the novel matches or differs from history, for the re-telling, and what one might see at the modern site of the battles described in the novel.  One series of historical novels is set in the American Civil War.  He wrote a nonfiction book on the battle of Waterloo, in addition to the fictional story of the famous battle in the Sharpe Series.  Two of the historical novel series have been adapted for television; the Sharpe television series by ITV and "The Last Kingdom" by BBC.  He lives in the US with his wife.  He alternates between Cape Cod, Massachusetts and Charleston, South Carolina.

Second Sea Lord: The Second Sea Lord (2SL), originally titled Second Naval Lord in 1830 the post was restyled "Second Sea Lord" in 1904 he is one of the most senior admirals of the British Royal Navy, responsible for personnel and naval shore establishments.  He is based at Navy Command, Headquarters.

Supporting paragraphs: Sea Lord (novel) Bernard Cornwell
Answer: the battle of Waterloo