China's President Xi Jinping rode in a gilded carriage to Buckingham Palace with Queen Elizabeth II past protesters on Tuesday at the start of a visit to Britain expected to focus on massive business deals.
Thousands of supporters cheered and waved Chinese flags as the elaborate procession rode past, while around 200 campaigners booed and waved placards attacking China's human rights record.
Xi also addressed parliament in a rare honour for visiting dignitaries, promising to lift relations between Britain and China to "a new height".
Prime Minister David Cameron's office said the visit will secure trade and investment deals worth more than £30 billion (40 billion euros, $45 billion) and lead to the creation of more than 3,900 jobs.
The most keenly awaited deal is an agreement for a new nuclear power plant in Britain in which French business daily Les Echos said China could take a one-third stake together with energy giant EDF.
The Chinese leader also took tea with Prince Charles, a friend of the Dalai Lama and who will not be attending a state banquet for Xi later on Tuesday in what has been widely interpreted as a diplomatic snub.
Cameron has been accused by some observers of kowtowing to China in a bid for investment and the visit comes at a particularly sensitive time as thousands of jobs are being cut in Britain's steel sector, partly due to low Chinese steel prices.
- 'Stand up for democracy' -
Leading Hong Kong pro-democracy activist Joshua Wong, 19, who attended a protest against Xi near Buckingham Palace, told AFP that the prospect of Chinese cash "has blinded the eyes of David Cameron".
"I just hope the British government and the British people can stand up for democracy because so many people in China are silenced and cannot stand up."
At the protest, campaigners waved the Tibetan flag and held placards reading: "End the Crackdown" and "Cameron: Don't Trade Away Human Rights".
But they were outnumbered by thousands of pro-Chinese demonstrators sporting hats, T-shirts and flags.
They watched on as dragon dancers and musicians created a carnival atmosphere on the Mall, the wide road leading to Buckingham Palace.
The four-day state visit includes a trip to Downing Street, Cameron's country residence Chequers, and even Manchester City football club on Friday, in a city that is keen to attract more Chinese investments.
In a sign of increasingly close business ties, the People’s Bank of China on Tuesday launched a yuan-denominated bond in London for the first time as it seeks to internationalise its currency.
The sale worth 5.0 billion yuan (690 million euros) offered a yield of 3.15 percent and was said to be the first time that a yuan-denominated bond auction has taken place outside of China and Hong Kong.
- 'Strategic opportunity' -
Cameron heralded the visit as "a very important moment for British-Chinese relations," but promised to address the protesters' concerns.
His spokeswoman told reporters Monday that "nothing is off the table" and insisted that he would raise human rights with Xi.
"By developing a strong and engaged relationship with China based on an approach of constructive engagement, that means we are able to talk to them about issues where we might differ," she said.
Cameron has also promised to lawmakers that he would take up the issue of Chinese steel prices.
Britain's courtship of China is being masterminded by finance minister George Osborne, Cameron's closest ally and a favourite to succeed him as prime minister, who spent five days in China last month.
While Britain's economy is growing, Osborne is currently implementing a package of austerity measures as he seeks to reduce a record deficit.
The visit comes amid increasing evidence that China's economy, the world's second-largest, is slowing down.
Official figures Monday showed it grew 6.9 percent in the third quarter of this year -- its slowest pace since 2009.
But Rajiv Biswas, Asia-Pacific chief economist at analysts IHS Global Insight, called the visit "a very important strategic opportunity" with China still forecast to become the world's largest economy by 2027.
The Chinese-British relationship has been rehabilitated since Cameron met the Dalai Lama in 2012, sparking an angry response from Beijing.