Emperor Akihito will become first Japanese monarch to abdicate in more than 200 years

The imperial palace grounds in central Tokyo are bathed in spring sunshine. Joggers completing circuits of the moat artfully dodge groups of foreign tourists. Office workers tuck into lunches of onigiri rice balls and tea.

On the other side of the moat, hidden behind lines of trees, the palace is preparing for a historical transition. Early in the evening of 30 April, Emperor Akihito will enter the building’s state room and, in the presence of the grand chamberlain, the prime minister and other senior politicians, become the first Japanese monarch to abdicate in more than 200 years.