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 & Partners 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.

中文翻译：

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“灵活的朋友”：十五世纪的汇票理论与实践†

汇票是中世纪后期国际金融界最重要的书面工具。使用 1436-8 年布鲁日和伦敦的 Filippo Borromei & Partners 的分类账中记录的近 2,000 张汇票、反对汇票和建议书的证据，我们认为这是一种比以前灵活得多的工具被认为。票据的到期日可以通过协议改变，而不必使用标准的远期期限，分期付款发生，大大延长了“贷款”的期限。在实践中，汇率每天都在变化，并且在当天本身内变化，而提供票据作为履行其他合同的担保。我们还证实了其他历史学家的论点，即这种工具的主要目的是在西欧之间来回转移资本，通常沿着众所周知的轴线，例如伦敦到威尼斯或布鲁日到巴塞罗那，进行交换和重新改变。在博罗梅的行动中只扮演了一个极小的角色。就像 100 年后的里昂博览会一样，“灵活的朋友”帮助国际、区域和地方贸易和金融世界运转起来。