I'm working on a new book set around Napoleon's invasion of Egypt. At present (in my very first draft) it has this paragraph:
On Thursday 28 June, Burke and William walked as usual to the granite column and saw, but a few miles offshore, the sails of a naval squadron. Burke focused the telescope and saw, to his relief, not the tricolore of France but ...
I was about to write 'the White Ensign' when I thought to check. And yes, the modern White Ensign was only introduced as the standard flag for British warships in 1864. Thank you Wikipedia. Also courtesy of Wikipedia we have:
"Ships flew the colour of ensign corresponding to the squadron to which they were attached, which was in turn determined by the seniority of the admiral under whose command the ship sailed (a rear admiral of the red was senior to a rear admiral of the white)."
At the time of the Battle of the Nile, Nelson (who commanded the British force) was Rear Admiral of the Blue, so my sentence now ended with 'the Blue Ensign'. At this point a friend (well, he was a friend then) pointed out that the Blue squadron was generally assigned to patrol the Pacific. (Hence, he said, the fact that the Australian and New Zealand flags are based on the Blue Ensign.) Was I sure that it was the Blue squadron at the Battle of the Nile? And, to worry me further, he produced a painting showing one of the ships involved flying the White Ensign.
I shouldn't have let that painting bother me. Paintings are not photographs and battle pictures were very seldom done by artists who were actually at the scene. Sometimes I have seen quite famous paintings of incidents that I have researched thoroughly, and the paintings are simply wrong. In this case, I have had a look at a couple of paintings that were done not that long after the events. 'The Destruction of 'L'Orient' at the Battle of the Nile' is quite a famous painting done early in the 19th century and it shows a Red Ensign. Thomas Luny's much reproduced painting shows a White Ensign.
Still, there was clearly room for doubt, especially as none of the contemporary paintings I found had a Blue Ensign. So I started through the accounts of the battle. Most serious histories point out that Nelson was an Admiral of the Blue, but they say nothing about his ensign. I even found a contemporary account by someone who was there and who had logged every incident his ship was involved in, but, of course, he would have assumed that anybody reading his work would know what the colours were, so he doesn't mention them.
Finally, after a fruitless couple of hours, I decided to stick with the Blue Ensign. But I might call in on the National Maritime Museum to make sure.
And what difference does all this research make to the finished novel? One word. One word in a paragraph which may not even survive to the final draft.
And that, my friends, is why historical novels take so long to write and are worth every penny of their pathetically inadequate cover price.