Brink of peace? Japan's Shinzo Abe called on to play mediator in Iran

What is Shinzo Abe doing in Tehran? The first visit by a Japanese prime minister to Iran in 40 years follows the recent state visit by Donald Trump to Tokyo. Trump and Abe enjoy strong relations. Japan is not a signatory of the nuclear deal from which the US walked away from last year and has had to bow to US warnings not to buy Iranian oil. So is Trump willing to shrug off his most hawkish allies in the region – the Saudis and the Israelis – to try to do a deal with Iran?