Boris Johnson became noticeably hot under the collar, probed on China's human rights record in a tough interview on a visit to the country - and challenged as to whether he could even say the name of the Dalai Lama.
The Mayor was asked by Sky's Dermot Murnaghan about China's human rights record and whether that was ever taken into consideration as the UK forged business ties with the nation.
But Johnson repeatedly side-stepped commenting on the issue.
"My job as Mayor is not to have a foreign policy but to get on and promote the interests of the greatest city on earth which is what we’re doing," he said.
"There are many interesting foreign policy problems around the world I could get involved in, whether or not that would improve global hopes for a resolution, I have my reservations.
"This is not the reason I’m here in China. I think we can respectfully move on to the real agenda which is intensifying links between London and China."
Murnaghan repeated the question five times in different forms, with Johnson refusing to even say the name of the Dalai Lama until he was asked directly to say it. China condemned Prime Minister David Cameron's decision to meet the Tibetan leader last year.
George Osborne and Boris Johnson are scheduled to spend a week in the country, promoting British business but also trying to attract more Chinese investment and research in the UK.
Despite being ruffled by the probing interview on Murnaghan's programme, the Mayor was in fine form at the rest of his official visits, joking about London's "communist" cycle scheme and his and Osborne's time at the Bullingdon Club in Oxford.
At an earlier event in Beijing's art district 798, Johnson said that he was proud London attracted so many Chinese students, joking that they are especially fond of the city's "beautiful communist bicycles", Boris Johnson joked as he kicked off a visit to China.
The factory-turned-gallery is one of the hippest spots in the capital, and Johnson was mobbed by students eager to snap a picture with him on their camera phones.
Johnson said: "Why is it that we are so lucky, so blessed in London, to have so many Chinese students?
"Is it because of the weather? You're laughing. Is it because we have so many wonderful French restaurants in London? Is it because we have so many beautiful communist bicycles on the streets of London?
"I'll tell you what I think it is. It's because we have more universities in London than any other city on Earth - 42 universities in London."
At the mayoral headquarters, Johnson, speaking to Beijing mayor Wang Anshun, said: "Obviously I'm delighted to hear that you were at Oxford. Did you enjoy your time at Oxford?
Wang said: "It was a very pleasant time for me and I learned a lot... Every night we would have a banquet session and at the end we would all sing songs. It was a very happy time.
Johnson replied: "We used to do that. The Chancellor and I used to do that too."
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Johnson is travelling with the chief executives of several large companies including Justin King of Sainsbury's and Marc Bolland of Marks & Spencer.
Osborne, who in the country to seal an £800 million plan for Chinese investment in Manchester Airport, said on Sunday the scheme would be one of the biggest projects since the building of the Olympic Park.
"I think it shows that our economic plan of doing more business with China and also making sure more economic activity in Britain happens outside the City of London is working," Osborne said.
"That's good for Britain and good for British people."