The Duke and Duchess of Cambridge have visited a charity working with destitute children who end up fending for themselves at a New Delhi railway station.
William and Kate, who are touring India and Bhutan, learned about the work of the Salaam Baalak Trust, which provides support for street and working children in Delhi.
The details of the visit were not announced in advance to avoid the visit attracting large crowds.
The trust supports youngsters, who end up at the major transport hub after running away from home or being abandoned by parents.
On average 6,600 children make their way to the train station every year and the charity helps by providing food and services like education and health.
Later the royal couple will have lunch with India's prime minister Narendra Modi.
William and Kate will sit down for informal talks with the Indian premier in New Delhi's Hyderabad House, a former royal residence of Maharajas that has hosted heads of state from across the globe.
The royal couple's official tour of India was announced after Mr Modi had lunch with the Queen during his visit to the UK in January.
The Duke and Duchess are on a seven-day tour of India and neighbouring Bhutan, their first visit to both countries.
On Monday, at a special garden party celebrating the Queen's 90th birthday, which falls next week, William paid tribute to his grandmother, describing her as a "wonderful great-grandmother'' for his children and very much his "boss''.
The Duke also said she was a "guiding force'' for her family.
The royal couple will later travel to Kaziranga National Park in the state of Assam, where over the next few days they will learn about the people and wildlife who inhabit the area.
Kaziranga is a World Heritage Site and a wildlife conservation area of global importance.
It is home to elephants, water buffalo, the endangered swamp deer, tigers, and two-thirds of the world's population of the Indian one-horned rhinoceros.
William has been campaigning for a number of years to protect endangered animals and park officials said yet another rhino had just been poached, bringing the total number of rhinos killed in Kaziranga this year to six.
Poachers shot the rhinoceros and, while it was still alive, sawed off its horn before fleeing before dawn Sunday, wildlife official Subasis Das said.
Once the dying animal was discovered, park officials rushed to try to save it but were unsuccessful, he said.
Prince William and his wife planned a visit to Kaziranga specifically to focus global attention on conservation.
The visit coincides with the Bohag Bihu festival, the celebration of the Assamese new year, and in the evening around a camp fire, the Duke and Duchess will meet local people and see dance and musical performances.