Since I've already been a pedantic wanker in this thread, I might as well dance...
"Colonel Shrapnel wasn't blown up, M. Guillotin died with his head on, Colonel Gatling wasn't shot. If it hadn't been for the murder of cosh and blackjack maker Sir William Blunt-Instrument in an alleyway, the rumour would never have got started." - Feet of Clay
Henry Shrapnel died a lieutenant-general, and was posthumously promoted to major-general. Convention is to use that final rank, however even if you are trying to be contemporaneous, he invented the eponymous shell while a lieutenant, so colonel is still wrong.
Richard Gatling was a medical doctor before becoming an engineer/inventor. He ran his engineering company during the US Civil War, and AFAIK he never served.
Likewise, Joseph-Ignace Guillotin was a French physician. Hence Docteur Guillotin, Monsieur Docteur, even Monsieur Medicins, but never Monsieur Guillotin. (Wikipoo says that Guillotin didn't actually invent the guillotine and opposed the death penalty, his family ended up changing their family name due to the shame. Also that a guy called Guillotin was guillotined.)
And finally, Willem Blunt was never knighted, the most he ever got was an OM. "Blunt Instrument" was also a nickname, not his actual surname. So, Willem "Blunt Instrument" Blunt OM. And he died after drunkenly falling off a horse, not being bashed in an alley.
Sir Terence Pratchett, OTOH, has an OBE and is fully entitled.