The Medici family of medieval Florence were one of the wealthiest families of all time. An exact calculation of their worth is impossible, as the family were secretive and records do not survive. But in terms of buying power and influence, the Medicis are up in the top league alongside the Carnegies, the Rockefellers and Bill and Melinda Gates.

And like these other families, the Medicis did more than just live lavishly. Their wealth was one of the engines that drove the great artistic and literary movement now known as the Renaissance. Western European art, philosophy and culture today owe the Medici family a great debt.

The family’s wealth came from the Medici Bank, founded in Florence early in the 14th century. Initially the Medicis were pawnbrokers, expanding into banking as the business grew. There were ups and downs, however, and not until the end of the century, under the leadership of Giovanni de Bicci dei Medici (1360-1429), did the bank begin to flourish. Giovanni won the business of the largest and most powerful borrower of the day: the papacy. Although in theory, Christian doctrine prohibited usury, the lending of money at interest, in fact, popes were always starved for cash, and happy to grant dispensations to bankers who could help them. The papal business was the foundation for the Medici Bank’s success.

Under Giovanni’s son, Cosimo dei Medici (1389-1464), the Medici Bank reached the height of its power. It became a diversified firm with divisions engaged in textiles, manufacturing and overseas trade. The Medicis also invested in mining and shipbuilding. Banking and trading offices were established around Italy and across western Europe, and there were agency relationships with traders in North Africa, Egypt and Persia. Medici agents bought fish in Iceland, pepper in Alexandria and silk in China, and shipped them across land and sea trade routes spanning two-thirds of the world. No other business of the time could come close to rivalling the Medici Bank in terms of size or income – or profit.

The Medici Bank was not a corporation, but rather a vast network of interlocking family partnerships. Most of the partners were Medicis or members of its client families such as the Portinari and the Tani, who were often related to the Medicis by marriage. Outsiders were sometimes given partnerships: such Giovanni d’Amerigo Benci, who became general manager of the bank and played a key role in its growth. But most of the vast wealth generated by this enterprise stayed in the family’s own hands.

Much of that wealth was invested. The family bought vast tracts of land in and around Florence and elsewhere in Tuscany. They invested in other businesses, especially in the wealthy trading cities of Genoa and Florence.

With the Medici, the boundaries between business and family were always rather hazy, and it seems that much of this investment was directed by Cosimo and his managers, even though it was other family members who stood to profit. It might be too strong to say that the Medici had a “family wealth management programme”, but we do know that members worked together and co-ordinated their investments. Two or three people might club together to buy a property and make a particular investment.

The family also donated vast sums to religious and civic institutions, mostly in Florence. Founding churches and monasteries was an act of piety; but it was also a way for men and women to flaunt their wealth. The Medicis did not just build such establishments, they also made them beautiful, commissioning the greatest artists and architects of the age. Michelangelo, Leonardo da Vinci, Rafael, Donatello, Ghiberti, Brunelleschi, della Robbia and Filippo Lippi headed the stellar list of artists who worked for the family.

In 1444, Cosimo used his wealth to try to heal the rift between the Roman Catholic and Greek Orthodox churches. At his own expense, he brought leading theologians and scholars from each side together in Florence, and urged them to negotiate. A concord was eventually hammered out, but the wider communion of Orthodox clergy rejected it.

The venture was an expensive failure, but it had a positive outcome. When Constantinople was captured by the Ottoman Turks eight years later, refugee scholars and writers came rushing back to Florence where they were sure of a welcome. Cosimo received them and gave many of them pensions. These refugee scholars, in turn, made an immense contribution to the scientific and philosophical advances of the later Renaissance.

With their own wealth assured, later generations of the family took less interest in the bank. Incompetent management led to its failure in 1494, but by this point most of the family had already moved on. They sought political power instead, and ruled as grand dukes of Tuscany until 1737, when Cosimo’s last male descendant, Gian Gastone dei Medici, died in Florence.

The Medicis were not entirely altruistic, and much of their wealth was used for selfish ends. But at the same time, it is hard to think of another family business who has made such an important contribution to western civilisation. The example of the Medicis shows how, when used wisely, a family’s wealth can change the world.