In 2013, the party issued its “seven unmentionables” — taboo topics for its members. The first unmentionable is promoting Western-style constitutional democracy. The Chinese characters for “Magna Carta” are censored in web searches on Sina Weibo, the country’s Twitter-like social media site.

Hu Jia, a prominent Chinese dissident, said he was not surprised that the exhibit had been moved off the campus. He said that Renmin University had close ties to the Communist Party’s training academy and that the principles the document stood for were contrary to the party’s. More important, he said, Chinese leaders may have been concerned that the exhibit would be popular and that “many students would flock there.”

“They fear that such ideology and historical material will penetrate deep into the students’ hearts,” Mr. Hu said.

The mysterious shift in venue took place the week before China’s president, Xi Jinping, is scheduled to make a state visit to Britain, the first by a Chinese leader in a decade. The British government has labeled 2015 a “golden year” in ties between the two countries, and it is eager to attract Chinese investment. Magna Carta’s China tour has been described as part of a deepening of ties. “I would like to take this chance to invite our friends across China to visit this important piece of our cultural heritage during this golden year of U.K.-China relations, and for it to spark further cooperation on rule of law and legal services,” said Britain’s ambassador to China, Barbara Woodward, according to a news release issued by the British government on Tuesday.

But securing a chance to see the document at the ambassador’s residence proved difficult on Wednesday. Registration had closed at 9 the night before, and the exhibit was open to the public for only three hours on Wednesday night, according to the embassy’s Chinese-language social media account. Mark Gill, executive director of the London-based Magna Carta 800th Committee, said the small room at the residence could accommodate only a limited number of people at a time.