Ai Weiwei and governments do not get on. Not long after having his passport returned to him by the Chinese government after four years without it, the artist and political dissident has lashed out at the British government for denying him a six-month visa, who are only letting him remain in the country for three weeks.

He posted this image of his rejection letter on his Instagram, along with another image containing a caption expressing his disbelief at the decision given that he is someone who has never been convicted of a crime. The ruling means that he may not be able to attend his exhibition being held at the Royal Academy of Arts in September.

Ai Weiwei accused the British government of taking "the position of those who caused sufferings for human rights defenders" and a friend of the artist, Liu Xiaoyuan, a human rights lawyer, told the Guardian that he was convinced Ai Weiwei does not have a criminal conviction.

"I don’t know which county’s understanding of criminal conviction the rejection is based on. If it’s the Chinese one Ai certainly does not have a conviction. As a lawyer I don’t think Ai has a criminal conviction. Under Chinese law Ai’s case ended in the police investigation stage and has not reached the court. The case does not have a court sentence and hence by Chinese standard, Ai doesn’t have a criminal conviction."

Another human rights lawyer also said "being subjected to residential surveillance is not the same thing as a criminal conviction." China’s President XiJinping visits London in October, a month after Ai Weiwei’s exhibition opens. It’s the first visit by a Chinese leader in a decade.

So why has Ai Weiwei’s six month visa application been rejected?