‘Your flexible friend’: the bill of exchange in theory and practice in the fifteenth century †

The bill of exchange was the most important written instrument in the international financial world of the later middle ages. Using the evidence of nearly 2,000 bills of exchange, protested bills of exchange, and letters of advice recorded in the ledgers of Filippo Borromei and Company of Bruges and London, 1436–8, we argue that it was a far more flexible instrument than has previously been thought. The maturity of bills could be changed by agreement rather than necessarily using the standard usance periods, and payment by instalments occurred, extending the length of the ‘loan’ considerably. In practice, exchange rates varied from day to day and within the day itself, while bills were offered as sureties for the fulfilment of other contracts. We also confirm the arguments of other historians that the main purpose of this instrument was the transfer of capital back and forth across western Europe, usually along well known axes such as London to Venice or Bruges to Barcelona, with exchange and re-change playing only a minimal role in the Borromei’s operations. As at the Lyon fairs 100 years later, the ‘flexible friend’ helped make the world of international, regional, and local trade and finance go round.