The three-day visit will focus on climate action, innovation and strengthening ties between India and the United Kingdom.
"When Prime Minister Narendra Modi meets with Their Royal Highnesses on Wednesday, they will be celebrating that partnership and discussing the areas of cooperation as we look to the future," Miller said at a press conference in Mumbai.
This will be William and Kate's first joint visit to India since 2016. Their programme will include engagements highlighting Indian cinema, cricket, sustainability and the growing economic relationship between the two countries.
During his visit, Prince William will participate in a gully cricket event and travel on the Mumbai Metro.
The Prince of Wales will also visit a production house, where he is scheduled to interact with Bollywood personalities. Princess Kate will visit a hospital in Mumbai as part of her engagements.
The royal couple's itinerary includes the Earthshot Prize awards ceremony on November 17, which will bring together environmental innovators, business leaders and international celebrities.
Earthshot Prize comes to India
The Earthshot Prize, founded by Prince William in 2020, will hold its sixth annual awards ceremony in Mumbai.
Fifteen environmental solutions across five categories have been shortlisted, involving 20 individuals. Five winners will each receive £1 million to expand their climate and environmental initiatives.
The event will be hosted by filmmaker Karan Johar, with appearances by Sachin Tendulkar, Alia Bhatt, Sonam Kapoor, Shreya Ghoshal and international celebrities.
The November 17 ceremony is expected to attract around 5,000 guests.
Miller said India's ability to develop and expand climate solutions made it an important partner for Britain.
"India's ability to innovate and scale solutions makes it a natural home for the Earthshot Prize, and a partner that we in the UK government are proud to work alongside in delivering global environmental and economic progress," he said.
The British official noted that India is already the world's third-largest renewable energy market and has ambitious plans to expand clean energy. He said UK-India climate cooperation is focused on three areas: clean energy, finance and resilience.
India-UK trade deal in focus
The visit also comes months after the landmark India-UK Free Trade Agreement came into force on July 15, 2026.
Miller recalled that Modi and British Prime Minister Keir Starmer had discussed building a modern partnership during their meeting in Mumbai last year.
The relationship has since expanded through the trade agreement, Vision 2035 and cooperation in technology, education, security and clean energy.
"In our landmark Free Trade Agreement, which came into force in July, it's no exaggeration to say this is a genuinely groundbreaking deal between our two countries that underpins that shared vision for the future. It's also India's broadest and deepest free trade agreement to date, and has opened new opportunities for business and consumers in both directions," Miller said.
The agreement is expected to increase annual bilateral trade by £25.5 billion and boost Britain's GDP by £4.8 billion annually in the long run, according to UK government estimates.