Inside the stables of Paleis Noordeinde in The Hague is a golden coach embellished with images of colonial offerings to Dutch rulers that many, including the current Dutch king, regard as a symbol of exploitation that, according to a new study, netted three Dutch rulers the equivalent of more than €545m (£465m). Historians calculated the staggering value of colonial profit for Willem III (also king of England, Ireland and Scotland), Willem IV and Willem V for a report published at the request of the Dutch parliament last week before a widely expected apology over slavery from the Dutch king. The study, State and Slavery, is the first to quantify the financial value to the Dutch House of Orange-Nassau of colonial trade that included enslaving at least 600,000 African men, women and children and between 660,000 and 1 million people from Asia to be tortured, exploited and robbed of their freedom and their names. It is a legacy for which Willem-Alexander is expected to present a formal apology in Amsterdam’s Oosterpark on 1 July, the festival of Keti Koti (breaking the chains), 150 years after Dutch slavery in effect ended. The €545m equivalent exceeded the money that the rulers, known as Stadhouders, took as heads of the state and military. Between 1675 and 1770, William III netted 1,094,998 guilders in his share of profits from the Dutch East India Company – the equivalent of €196m today. Raymund Schütz, a researcher at the municipal archives in The Hague, discovered the figures about the Dutch Stadhouders, appointed regents, last year in a private archive of Gerard van Vredenburch. This important figure in the Dutch East India Company was apparently hoarding and documenting secrets “like poker cards”, he said. “It was seen as something to be proud of,” said Schütz. “In some cases, they took enslaved people to the Netherlands to show off. It was a kind of conspicuous investment and consumption to show you were important, a kind of status symbol. These days, everybody is ashamed and it’s hard to imagine how it was seen at the time. But the main thing was making money.” Schütz said it was not yet known how much the Netherlands’ rulers profited from slavery between 1621 and its abolition on 1 July 1863 (followed by 10 years of compulsory employment for the enslaved). The Dutch king has commissioned a three-year independent study. Last year, the UK’s King Charles, then Prince of Wales, expressed “the depths of his personal sorrow” about suffering caused by the British slave trade, and in 2021 Germany offered €1bn in recognition of colonial-era genocide in Namibia. Last December, the Dutch prime minister, Mark Rutte, apologised for the government’s role and the “appalling suffering” caused to generations, and announced a €200m fund for awareness initiatives but no reparations or damages. A spokesperson for the Dutch royal household confirmed that Willem-Alexander would make a speech at the Keti Koti celebrations in Amsterdam – something widely expected to contain his own apology. Don Ceder, an MP for the Christian Union and a lawyer, has played a major role in stimulating government recognition. “I think that an apology from the king in his institutional role would [be of] enormous significance in the reconciliation process,” he said. “The Dutch royal family received a significant portion of her wealth through the slave trade … A sincere reflection upon that past could contribute to a shared future.” Descendants of the enslaved believe that recognition of the profit and wrongs of the past are long overdue, according to Linda Nooitmeer, president of the National Institute of the Dutch Slavery Past and Legacy (NiNsee), whose surname means “never again”. “The symbolic value of the king is so great that an apology is not just valued: it is self-evident,” she said. “In 2019, an investigation showed that 5% of Dutch GDP [in 1770] came from slavery. What the community thought, seems to be true.” Roy Kaikusi Groenberg, of the Honour and Recovery Foundation, a Dutch Afro-Surinamese organisation, was one among many who took the government to court last year to demand a careful apology. “It would mean that the king, in the name of the monarchy and the Dutch head of state, underlines a kind of recognition,” he said. “I’m not a psychologist, but I think this apology will be the start of another era, that it will bring a kind of peace. The relatives of the victims of slavery are right now confronted with the consequences of that behaviour: racism, discrimination, being undervalued, Black Pete [a festive tradition in the Netherlands in which people dress up in blackface]. If people in the Netherlands truly realise what happened and what still needs to happen, I do not think they will lack the will.” The golden coach may be retired until the Netherlands is a land of real equality, according to the king. But one way of achieving this is, in classic Dutch style, by sitting at a table. Across the country, organisations from the Rijksmuseum to police stations and town halls have organised hundreds of “Keti Koti Tafels” where, over a meal, different communities share personal stories about experiencing and tackling modern-day discrimination. “The aim is to bring people closer together,” said a spokesperson. “We want to increase awareness of the internal consequences of a slavery past, that sits in a collective archive of us all … black, white and all colours in between, sharing personal experiences. We share a society, we are all people and we need to come together.”