On Tuesday June 20 Mohammed bin Nayef, a powerful figure in Saudi Arabia’s security apparatus for the past two decades and the next in line to the throne, was summoned to meet King Salman bin Abdulaziz on the fourth floor of the royal palace in Mecca.

There, according to a source close to MbN, as he is known, the king ordered him to step aside in favour of the king’s favourite son, Mohammed bin Salman. The reason: an addiction to painkilling drugs was clouding MbN’s judgment.

“The king came to meet MbN and they were alone in the room. He told him: ‘I want you to step down, you didn’t listen to the advice to get treatment for your addiction which dangerously affects your decisions’,” said the source close to MbN.

The new details about the extraordinary meeting between the king and MbN that touched off the de facto palace coup help to explain the events that are reshaping the leadership of the world’s biggest oil exporting nation.