Israel does not allow international news organisations, including the BBC, into Gaza, making verifying what is happening in the territory difficult.
He said he was not a member of the Communist Party and his research had nothing to do with the military."They asked me what the relationship was between my research and China's defence affairs," he told the BBC then. "I said, how could breast cancer have anything to do with national defence? If you know, please tell me."
He believes he never stood a chance because the officials had already made up their minds. He recalled one of them asking: "Did Xi Jinping buy your suitcase for you?"What was surprising, or even shocking then, slowly turned normal as more and more Chinese students struggled to secure visas or admissions to study science and technology in US universities.Mr Cao, a psychology major whose research involves neuroscience, has spent the past school year applying for PhD programs in the US.
He had graduated from top-tier universities - credentials that could send him to an Ivy League school. But of the more than 10 universities he applied to, only one extended an offer.Trump's cuts to biomedical research didn't help, but the mistrust surrounding Chinese researchers was also a factor. Allegations and rumours of espionage, especially in sensitive subjects, have loomed over Chinese nationals at US universities in recent years, even derailing some careers.
"One of the professors even told me, 'We rarely give offers to Chinese students these days, so I cannot give you an interview," Mr Cao told the BBC in February.
"I feel like I am just a grain of sand under the wheel of time. There is nothing I can do."For Jade Bradford, from Hertfordshire, it was a life-long dream to attend Hay Festival.
As a communications and engagement manager for a social housing provider in south Wales, writing is Jade's second job.After growing up seeing the Guardian's Hay Festival supplement every year when her dad would buy the paper, this year she was in attendance as a Writer at Work.
"Publishing, it can feel like a closed door sometimes and it's hard to know who you need to speak to, what it is you actually need, how you get an agent," the 39-year-old said.She said if audiences at events like Hay Festival were not representative they may not know their books are not diverse enough, or "that they need to hear other voices".