Opponents say the red-flag waving crowd was there courtesy of the Chinese embassy - which offers incentives to overseas students to do their patriotic duty wherever Mr Hu travels.
If the Chinese leader had looked to his right, the cheers and smiles of the official welcoming party would have been replaced by angry scowls and jeers of those whose voices he does not allow to be raised back home.
Unlike in 1999 when his predecessor, Jiang Zemin, was forcibly shielded from visible signs of dissent by the Metropolitan Police, demonstrators were given free rein to vent their feelings yesterday. They did so noisily but politely.
Amid the protesters were those dismayed at the British Government's decision to greet the Chinese President with the pomp and pageantry of a state visit.
Typical of their stories of life in the old country was Tashi, 31, a monk who fled Chinese-occupied Tibet three years ago, spending three months in jail for participating in a peaceful protest in front of tourists. He was arrested and taken to a police station where he was beaten and then taken to prison.
"We didn't know what was happening or what was going to become of us. It was very frightening," he said yesterday as he defiantly held aloft the banned flag of his home country. After his release, he was hauled in regularly by the authorities for further questioning and threatened with life in jail. "I was lucky. My story is much easier than others," he explained. Torture and disappearances in Tibet, where President Hu ruled with an iron fist as Communist Party Secretary, are all too commonplace, he said.
It is a similar story for Dr Li Shao, now an academic at the University of Nottingham. As a practising member of the banned spiritual movement, Falun Gong, he has witnessed some of the worst of Beijing's repression.
Dr Shao said 2,800 of his fellow followers had died as a result of their beliefs. A further 200,000 had been interned in labour camps. Among them is his sister-in-law, an accountant from the province of Guangzhow, who was arrested after she gave a seminar on Falun Gong in London. She now works 14 hours a day in a flower factory for no pay.
"When she was seen meditating by the guards she was handcuffed by her wrists and hung from a door frame," he said. "The British Government has never raised the issue with China. Tony Blair has never even uttered the words Falun Gong to a Chinese leader," he said. Falun Gong supporters will mount a vigil outside Buckingham Palace for the duration of President Hu's stay. Last night, they watched as Mr Blair arrived for the official state banquet. They will watch as the Chinese leader sets out to Downing Street today for trade talks with the Prime Minister followed by another banquet at Guildhall. From their vigil, they will see the London Eye and Somerset House illuminated in red in honour of the Chinese guests.
Falun Gong tried yesterday to have the commerce minister, Bo Xilai, who is travelling with the party, arrested on suspicion of conspiracy to torture members of their religion in Liao Ning. The attempt, made before Bow Street magistrates' court, failed.
Ilyar Pakhirdin, 37, was waving a blue flag as the President passed. He first fell foul of the authorities while still at secondary school. He was arrested after sticking up a poster demanding freedom for his fellow Uyghurs and kept in prison for 15 days.
Located beyond the Great Wall of China, the 8.9 million Uyghurs do not consider themselves Chinese. But their sparsely populated land has become a base for nuclear testing, training and forced labour camps. Their culture, language and religion is being steadily stamped out, he said. He was regularly arrested and detained by Chinese authorities, eventually fleeing the country - leaving his wife and children behind. "How can they treat President Hu on a par with George Bush or President Putin? I could not believe the Queen would receive him in this way," he said.
* 1978: Romanian dictator Nicolae Ceausescu is awarded an honorary Grand Cross of the Most Honourable Order of the Bath. Britain rescinded the honour in 1994.
* 1979: President and Mrs Suharto are received in Britain despite concerns over the detention of political prisoners and the occupation of East Timor.
* 1985: President Hastings Banda of Malawi, who banned opposition parties and ruthlesly crushed dissent, is rewarded with a state visit.
* 1989: President Babangida of Nigeria is conferred with the Knight Grand Cross of the Bath (GCB) by the Queen.
* 1994: Zimbabwe's Robert Mugabe is entertained at a state banquet at Buckingham palace and awarded an honorary GCB. Britain sought the return of the medal in 2003.
* 1999: Jiang Zemin becomes the first leader of communist China to make a state visit.Reuse content