Given that the Trojan War is supposed to have occurred around 1200 BCE (highly speculative), and the first mention of Brutus we know of is in 900 CE, that’s a gap of 2100 years between the event and the first time someone wrote it down. That alone should give us pause. (To be clear, Isidore of Seville did declare a parallel theory in the 7th century CE, based on another Roman general named Brutus, but it’s an equally suspect theory).

What Gregory of Monmouth is doing is actually quite elegant from a literary perspective. As the Romans used the legendary hero Aeneas to establish a continuity between themselves and the Trojans, the medieval Britons are using the legendary hero Brutus of Troy (usually a relation of Aeneas) to create a parallel link between themselves and the Romans. In one swoop Gregory is declaring Britain to be the heir of both Rome and Troy, but it’s an ideological claim, not a historical one.