Yes, good old Geof was a great story teller and inventor and he may have invented Brutus, but I don't think he invented the Trojan connection entirely.

Virgil tells what happened after the fall of Troy in his Aeneid which tells of the founding of Rome. The Romans liked to believe that they were descended from displaced Trojans. So what?

The link with Britain is that (whatever the Iron Age people of what we now call Essex called themselves) - the Romans called them Trinovantes. I understand that "Trinovante" is Tri Novante which means New Troy. I reckon Geof new that and it also is another example of incomers naming residents. Many of the Iron Age tribal names were bestowed upon them by the Romans. Obvious parralel with tribal names of the American Indians - some were native like Lakota and Oglala others were European and given to reflect personal characteristics eg Blackfeet and Nez Perce (pierced nose)