David Cameron has promised China's leadership that there will be "very open competition" for investments in Britain's HS2 high-speed rail link.
The Prime Minister said he made the pledge during talks in Beijing with President Xi Jinping and Premier Li Keqiang, who expressed an interest in putting Chinese money behind the controversial project, which will link London with cities in the Midlands and North of England.
His comments came during a question session at Shanghai's Jiao Tong university, where he assured students who raised concerns about Britain's visa system that there was "no limit" on the numbers of Chinese who could study in the UK and voiced his ambition to raise numbers from the current 105,000.
The second day of Mr Cameron's visit to China was devoted to business, as the PM welcomed the announcement of an £80 million investment in the manufacture of black London taxis in Coventry by Chinese car firm Geely, posed for a "selfie" photograph with Jack Ma, the creator of China's biggest online retail site, and hailed a treaty which will allow easier access for UK films to cinemas in a country which is opening new screens at a rate of seven a day.
Addressing a business lunch in Shanghai, Mr Cameron said his message to Chinese companies was: "If you are investing in Britain, invest more. If you are thinking of investing in Britain, come and find us. You will get a warm welcome."
But there was a less warm welcome for the Prime Minister from the state-run Global Times newspaper, which said in an editorial: "We've discovered that Britain is easily replaceable in China's European foreign policy. Moreover, Britain is no longer any kind of 'big country', but merely a country of old Europe suitable for tourism and overseas study, with a few decent football teams."
Mr Cameron stressed Premier Li's characterisation of Britain and China as "indispensible partners" as an indication of the deepening bonds between the two countries.
But he also described Britain as a "small island" himself, as he explained to students why the Government is having to fight to build one high-speed rail line, while China has successfully completed 6,214 miles (10,000km) of track.
"The problem in a small country like the UK is obviously infrastructure decisions are very controversial because we are a small and relatively crowded island so the use of space for infrastructure is always controversial, whether you are trying to build airports or railway lines or new roads," he said.
"My Government has taken a very clear view that the countries that will succeed in the future are the countries with the most modern infrastructure.
"We think we have a lot to learn from China in this regard because of the success of your high-speed rail. I said to your President and Prime Minister yesterday that, just as we welcome Chinese investment into nuclear power and other infrastructure, so there will be very open competition to provide the infrastructure for our networks, so we welcome Chinese investment into that as well."
Mr Cameron acknowledged that obtaining visas was "a source of frustration" for Chinese students, and said he wanted to make it easier for students and tourists from China to come to the UK, as well as to increase the number of Britons studying in Chinese universities from the current 4,000.
The PM was quizzed by students on his own experiences at Oxford University, and revealed that his former politics tutor, Professor Vernon Bogdanor, "still sends me emails criticising my work".
He admitted finding his weekly grilling by MPs at Prime Minister's Questions "a form of torture".
But he risked annoying his Chinese hosts by highlighting the benefits of forcing senior ministers to justify their actions in public on a regular basis.
"It makes the Government accountable," he said. "It means the whole of the Government has to account for itself through that one person."
Issues of free speech have hung over Mr Cameron's visit, after a journalist from news agency Bloomberg was excluded from his joint appearance with Mr Li because of a long-running spat with the Chinese authorities.
The Prime Minister himself signed up to microblogging website Weibo - the Chinese equivalent of Twitter - and quickly recruited 160,000 followers, one of whom pointedly asked him: "When will President Xi open a Weibo account?"
Mr Cameron told students in Shanghai that he had raised human rights issues in his talks with the Chinese leadership. But when listing the global hotspots which they had discussed, he named Syria, Iran and Burma but did not mention Tibet.
Downing Street said the PM's visit, at the head of the largest UK business delegation ever to visit China, has already resulted in deals valued at £5.6 billion which could create 1,500 jobs in Britain.
They ranged from a £4.5 billion contract for Jaguar Land Rover to supply 100,000 luxury vehicles to smaller deals for Moulton to provide bicycles for the Chinese market and even a contract for Manchester-based Sweet Mandarin foods to sell Chinese sauces to the Chinese.
Many British products were on display at today's lunch at the Shanghai exhibition centre, where scenes from James Bond's Skyfall and ITV drama Downton Abbey played on giant screens.
Guests gasped and took out their camera-phones at a surprise appearance by puppeteers from the National Theatre operating a lifesize and startlingly lifelike horse model from hit production War Horse, which is to be given a run-out on the stage in China following an agreement with the National Theatre of China.
Mr Cameron won warm applause from Chinese guests as he told the lunch about plans for same-day visas for business visits to the UK.
"My Government is committed to working with the Chinese government in a way of mutual respect and understanding to deepen these relations and remove barriers to trade and investment and partnership between our two countries," he said.
And he rounded off his speech by attempting a phrase in Mandarin - "Wei shuang fang you li", or "in both sides' interest".