Modi arrived at Buckingham Palace for lunch Friday in a Jaguar, the iconic British car brand owned by India's Tata Motors — a symbol of the close relationship between India and its former colonial ruler.
Later, Modi was greeted as a celebrity by tens of thousands of supporters waving Indian flags and Union Jacks during a high-energy rally at London's Wembley Stadium — more usually home to rock concerts and England's national soccer team.
He was introduced onstage by Prime Minister David Cameron, who has often been by Modi's side on the trip, a sign of how important Britain considers the visit.
The crowd cheered when Cameron said, "it won't be long before there's a British Indian prime minister in Downing Street."
Modi's ambitious plans to modernize India and his pro-business agenda have won him many fans among the 1.5 million people of Indian origin in Britain.
"In a country that has suffered a lot because of corruption and misadministration, Modi is regarded as someone who is a clean politician and is somebody who delivers," said Manoj Ladwa of the Europe India Forum, which organized the Wembley rally.
But the Hindu nationalist politician has also been met by protests from Sikhs, Muslims, human rights groups and others who accuse him of failing to stop growing religious intolerance and violence in India.
Britain and India have announced major business deals and cultural exchanges during Modi's trip, which ends Saturday, including an Indian tour for historic British texts such as the Magna Carta and the opening of a Madame Tussauds wax museum in New Delhi.
And on Friday William and Kate's Kensington Palace office said the royal couple would make their first visit to India in spring 2016.
Modi is being treated to full British pomp and ceremony on the three-day visit. On Thursday he was welcomed by ranks of Scots Guards, saw a ceremonial fly-past by the Royal Air Force Red Arrows aerobatic team and gave a speech to Parliament before spending the night at Prime Minister David Cameron's country retreat Chequers.
Cameron said Modi's visit cemented a "modern, dynamic partnership" between the world's fifth-largest economy — Britain — and India, which will soon rank third.
The two countries have announced 9 billion pounds ($14 billion) in business deals, including a 2 billion pound British investment in solar power in India and more than 1 billion pounds' worth of London-issued bonds to fund the expansion of India's rail network and other projects.
Modi swept to power in 2014 on promises to develop India's economy and root out the corruption and incompetence that had crippled the previous government. But he has also been accused of failing to stop attacks on religious minorities, and his BJP party suffered a recent drubbing in an important state election widely seen as a referendum on Modi's popularity.
(AP)
British Prime Minister David Cameron, right, walks in the garden at his official country residence Chequers in Wendover, England, with his Indian counter-part Narendra Modi on the second day of his official visit to the UK, Friday Nov. 13, 2015. Modi and Cameron both vowed Thursday to use U.K. knowhow and investment to help modernize the world's largest democracy, India.
Britain's Queen Elizabeth II meets with Indian Prime Minister Narendra Modi at Buckingham Palace, London, on the second day of his visit to the UK, Friday Nov. 13, 2015. Modi is in Britain for three days of cultural events and high level political and business meetings.
Britain's Queen Elizabeth II meets with Indian Prime Minister Narendra Modi, right, at Buckingham Palace, London, on the second day of his visit to the UK, Friday Nov. 13, 2015. Modi is in Britain for three days of cultural events combined with high level political and business meetings.