Factual error: All of the Lydia's lieutenants are wearing epauletes on their left shoulders.only lieutenant commanders were permitted to wear one on the left shoulder, while the right shoulder was reserved for captains of less than 3 years' seniority.
Factual error: The film is set in 1807 and Arthur Wellesley is referred to as the Duke Of Wellington. He didn't become a Duke until 1814.
Factual error: As the Natividad appears, the lookout signals "ship's royals horizon, southeast" by using a shuttered lantern and morse code.unfortunately, neither the lantern nor the code had been invented in 1807. Flag hoists during the day, and rockets and flares at night were the methods of signaling at that time.
Plot hole: When Hornblower arrives home from the Pacific, he meets his son, a baby in a cradle. He is given the Sutherland, sails to Spain, is captured and escapes, and returns to England a hero..all in under a year. However, upon arriving in Portsmouth to see the Admiral, he visits his son, now a child of 3 or 4.
Other mistake: The day after informing Lady Barbara that he was married, Hornblower, in a rush to get home, orders the t'gallants set. But the ship, as shown in the prior scene, already has them set.
Factual error: Upon his triumphant return in Lydia, Admiral McCartney tells Hornblower, "We're giving you a 74. A Frenchman we captured, renamed the Sutherland." According to C.S. Forester, the Sutherland was actually a Dutch 74, originally named the Eendracht, thus explaining its shallow draught, as commented on during the captain's meeting aboard Leighton's flagship.
Continuity mistake: When the Sutherland engages the four French ships, her masts are shot to doll rags, with the upper masts and fighting tops plunging to the deck. However, the lower shrouds and ratlines, which are attached to the tops, remain intact.
Factual error: When Hornblower orders "Beat to Quarters" before the second engagement with the Natividad, none of the cannons are bowsed up. During normal ship operations, the muzzles are raised up above the gunports and the guns are bowsed tightly against the ship's side to prevent the weapon from rolling to and fro and causing damage.
Plot hole: During the second engagement with the Natividad, Hornblower is advised that the surgeon is dead. The duty station of a surgeon in battle is in the cockpit on the orlop deck, far below the waterline. The odds of a cannonball penetrating there would be longer than its penetrating the cable tier.
Factual error: The lower masts on a 74-gun ship of the line are made up of numerous trees, with metal bands used to clamp them into a single unit. Upper masts were usually made from a single tree and did not require banding. During the engagement with the 4 French ships, sections of mast plunge onto the decks, and all of them are banded with hemp.
Factual error: During the battle with the four French warships, Hornblower gives the command, "Port your helm", and the quartermaster complies, turning the wheel to the left. Unfortunately, this would result in the Sutherland turning starboard, vice larboard, since the rudder would have been turned to port.