Pre-EU free trade: a tale of Offa and Charlemagne
Offa was the contemporary of Charlemagne. His policy interlaced with that of Europe; he was reputed to be the first ‘King of the English’ and he had the first quarrel since Roman times with the mainland.
Charlemagne wished one of his sons to marry one of Offa’s daughters. Here we have an important proof of the esteem in which the Englishman was held. Offa stipulated that his son must simultaneously marry a daughter of Charlemagne. The founder of the Holy Roman Empire appeared at first incensed at this assumption of equality, but after a while he found it expedient to renew his friendship with Offa. It seems that the ‘King of the English’ had placed an embargo upon Continental merchandise, and the inconvenience of this retaliation speedily overcame all points of pride and sentiment. Very soon Offa was again the Emperor’s ‘dearest brother’ and Charlemagne is seen agreeing to arrange that there should be reciprocity of royal protection in both countries for merchants, ‘according to the ancient custom of trading’.
From Winston Churchill’s History of the English-Speaking Peoples