The Queen and Duke of Edinburgh formally welcomed China's President Xi Jinping to Britain with a ceremony full of pomp and pageantry.
At London's Horse Guards Parade - Henry VIII's former jousting yard - the two heads of state shook hands ushering in closer ties between Britain and China.
Among the dignitaries watching was David Cameron who has hailed the visit as an "important moment'' in relations between the two nations, but the Prime Minister is facing pressure to raise concerns over human rights issues and the "dumping" of cheap steel with the Chinese leader.
Ministers expect more than £30 billion of trade and investment deals to be struck during the four-day visit that has seen see the UK pull out all the stops to court the leader of the world's second-largest economy.
Critics have warned that Britain will "rue the day'' it forged deeper ties with China and accused the Government of acting like a "panting puppy'' in its relations with the country.
But Foreign Secretary Philip Hammond insisted the move was in the national interest.
Mr Xi and the Prince of Wales arrived in a chauffeur-driven limousine and behind them in another car was the Duchess of Cornwall and the president's wife Peng Liyuan.
The party had made the short trip from the exclusive Mandarin Oriental hotel in nearby Knightsbridge and as their car arrived on the parade ground the Queen and Philip turned to face them.
The muffled sound of a 41-gun royal salute rang out as the King's Troop Royal Horse Artillery in nearby Green Park, fired the volleys.
The Queen introduced the President to leading figures from her Government and national life including Mr Cameron, Home Secretary Theresa May, Alan Yarrow, the Lord Mayor of the City of London and Metropolitan Police Commissioner Sir Bernard Hogan-Howe.
Military top brass were also presented to China's leader - General Sir Nicholas Houghton, Chief of the Defence Staff, Vice Admiral Sir Philip Jones, The Fleet Commander, General Sir Nicholas Carter, Chief of the General Staff, Air Chief Marshal Sir Andrew Pulford, Chief of the Air Staff.