Where is Erich von Däniken when you need him? Then again, Nero Claudius Drusus (12BC) did take a fleet of almost 1000 ships into the North Sea. Wouldn't be impossible for one to drag anchor out to sea or get "blown off course." Pesky Romans.

btw there's an entire wiki of these things:
https://en.wikipedia.org/wiki/Pre-Columbian_trans-oceanic_contact_theories

btw2 More KFC in London than you can shake a drumstick at. One just down the way from the Natural History Museum. Mmmmm cultures!