Here are the latest developments:
A short while ago, PM Modi had lunch with Britain's Queen Elizabeth at the Buckingham Palace.
At the Wembley, seats filled up fast for PM Modi's reception. The famous football field at the stadium has been covered to protect it, with a stage at one end with a huge tricolour backdrop.
UK Prime Minister David Cameron will introduce PM Modi, who will then make a speech.
Rapper Jay Sean, singers Alisha Chinai and Kanika Kapoor are performing, as are the London Philharmonic Orchestra and many school children. It is being billed as the biggest reception by NRIs for PM Modi yet.
As the PM lunched with the Queen, Britain announced, "The Duke and Duchess of Cambridge will visit #India in the spring of 2016, at the request of HM's Government." Details will be announced closer to the time of the visit.
On day 2 of his trip, PM Modi also met top industrialists at a CEO's forum. "We are confidently, consistently and ceaselessly working to integrate our economy with the world," PM Modi said.
He has also held multiple meetings with his host and British counterpart David Cameron, who hosted PM Modi last night at his country retreat, a 16th century mansion in Buckinghamshire.
PM Modi landed in London yesterday and held bilateral talks with Mr Cameron. After the talks, India and UK announced deals worth 9 billion pounds. The two countries have also signed a civil nuclear pact.
Confronting questions from the British media on "growing incidents of intolerance" back home, PM Modi said his government was committed to protecting every citizen's freedom. "India is the land of Buddha and in our society, we don't accept unconstitutional things. The law will deal with these severely," the Prime Minister said.
The PM also addressed British MPs taking a strong stand on terror and reaffirming India's stance on climate change. "We need a social movement against extremism in countries where they originate," he said.