Andy Burnham has gone further than any previous prime minister towards offering a formal apology for Britain’s role in the transatlantic slave trade, in a Guardian article ahead of a Commonwealth leaders’ summit where the subject is expected to dominate.

As he prepares to fly to the Caribbean next week, the prime minister said he was open to calls for an official apology on behalf of the state and offered formal talks to those affected, including individual countries and campaign groups at home and abroad.

Burnham wrote: “The Britain I believe in is confident, decent and brave.…