Enslaved African people were seared with hot metal brands bearing the royal crown, according to research by historians who have documented the monarchy’s centuries-long involvement in Britain’s slave trade.

The kings and queens most heavily involved were those who ruled after the monarchy was restored in 1660. The Register of British Slave Traders is the most comprehensive research project into the investors in the country's trafficking of enslaved African people. Its publication will further inform calls for the king to finally acknowledge the monarchy’s deep involvement in the trade.

In response to the Guardian’s reporting of the new research relating to the monarchy, a spokesperson for King Charles said he was 'grateful to all those undertaking academic work in this area and thus contributing to the debate about how such issues might best be addressed'.

• The royal crown branded on enslaved Africans: Britain’s monarchy and the slave trade