Indian Prime Minister Narendra Modi is meeting the Queen prior to speaking to thousands of supporters a mass rally on the second day of his UK visit.
He is having lunch at Buckingham Palace before later taking part in a rally at Wembley Stadium, where he is expected to be joined on stage by David Cameron.
Earlier, Modi met UK and Indian business leaders in No 10, having announced £9bn in commercial tie-ups.
Modi's three-day UK visit is the first by an Indian PM in a decade.
He has described India's relationship with the UK as being of "immense importance", while Prime Minister David Cameron has said the countries need to create "one of the leading global partnerships".
But Modi's appearances have also attracted protest over allegations of religious persecution and a reduction in civil liberties since he came to power.
MODIMANIA: INDIA'S SUPERSTAR PM
- Narendra Modi is seen as a divisive politician - loved and loathed in equal measure
- He is leader of the Bharatiya Janata Party (BJP) and took over as PM in May 2014 after leading his party to a spectacular general election win
- He served as the chief minister of Gujarat from 2001 and is regarded as a dynamic politician who helped make the western state an economic powerhouse
- But he is also accused of doing little to stop the 2002 religious riots when more than 1,000 people, mostly Muslims, were killed - allegations he has consistently denied
- His 18 months in power have been somewhat controversial amid concerns over rising social tensions and intolerance in India
- Modi is known as a brilliant public speaker and is very popular among Indian communities abroad - 60,000 people are expected to fill Wembley Stadium to hear him speak
The businesses deals between the UK and India were announced after Modi was hosted at Cameron's country residence Chequers.
Number 10 said 1,900 jobs had been created or safeguarded as a result of the tie-ups in the retail, logistics, energy, finance, IT, education and health sectors.
Up to 60,000 are expected to attend the event at Wembley, which will include performances from Indian and British stars, a fireworks display and a speech by Modi.
The event is expected to be a celebration of the Indian diaspora's contribution to the British economy.
BBC Hindi's Nitin Srivastava said there would be a "lot of dance, pomp and show", with expectations of a crowd of more than 50,000.
On Thursday, in the first speech by a serving Indian PM to Parliament, Modi said UK and India were "two strong economies and two innovative societies" but he said their relationship "must set higher ambitions".
The first day of Modi's visit also attracted protests outside Downing Street directed against a number of issues including claims of religious persecution, and interference in Nepal
Amnesty International has urged Cameron to intervene over a "fevered crackdown on critics under way in India".