IT IS little more than a week since Ai Weiwei, a Chinese artist and perpetual irritant to his country’s authorities, was given back his passport, marking the end of a four-year travel ban. Mr Ai has already made arrangements to visit Europe, stopping first in Germany. But on July 30th it emerged that the visa for his proposed onward trip to Britain would be unexpectedly limited, after Mr Ai received a letter from a bureaucrat saying that his travel would be restricted because of a failure to own up to his “criminal” past. Mr Ai is used to such interference. The surprise was that the letter came not from the Chinese authorities, but from the British.

In a letter from the UK Visas and Immigration authority dated July 29th, which Mr Ai uploaded to his Instagram account, a Beijing-based “entry clearance manager” writes: “You have applied for a six month business visit visa, but on this occasion your visa has been restricted to the requested dates of travel on your visa application form”. The reason given is that Mr Ai answered “No” to a question asking whether he had previous convictions. “It is a matter of public record that you have previously received a criminal conviction in China, and you have not declared this,” the letter states.

Mr Ai says he has no such conviction. The letter may be referring to a fine against the artist for tax evasion, which was upheld in 2012, though by Mr Ai’s account those proceedings were not criminal but civil (and more than a little political). British authorities have yet to comment on the details of the case. The home secretary, Theresa May, is “looking into” the matter, a spokeswoman says.

The jobsworthiness of the officials running Britain’s pricey, petty visa system should not be underestimated. But the timing of Mr Ai’s proposed visit has made some wonder if there is more to the restriction than mere bureaucratic pedantry. Rather than be given the six-month visa for which he applied, Mr Ai has been given permission to be in Britain only between September 9th and 29th. That means he will be safely out of the way by October, when London is expecting another Chinese visitor: Xi Jinping, the president.

Mr Xi’s state visit, the first by a Chinese president in ten years, is a chance for the two countries to build on a promising commercial relationship. They have been getting on famously in recent years, having apparently overcome a falling out in 2012 when David Cameron, Britain’s prime minister, had a meeting with the Dalai Lama in London. The last thing British officials want now is for a different troublemaker to upset the October meeting. Mr Ai’s strange visa restriction may be completely unrelated. But it is a curious, and convenient, coincidence.