Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge, visit the Taj Mahal on April 16, 2016 in Agra, India.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge pose in front of the Taj Mahal on April 16, 2016 in Agra, India.

Britain's Prince William and his wife Catherine, the Duchess of Cambridge, look at the Taj Mahal in Agra, India, April 16, 2016.

Britain's Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge walk through the grounds of The Taj Mahal in Agra, India on April 16, 2016.

Britain's Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge, walk during their visit to The Taj Mahal in India on April 16, 2016.

Britain's Prince William, along with his wife, Kate, the Duchess of Cambridge, arrive to see the Taj Mahal in Agra, India, Saturday, April 16, 2016.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge, bid farewell at Paro Airport before boarding their flight to Agra for their visit to the Taj Mahal on April 16, 2016 in Paro, Bhutan.

Catherine, Duchess of Cambridge attends a reception celebrating UK and Bhutanese friendship and cooperation at the Taj Hotel on April 15, 2016 in Thimphu, Bhutan. The Royal couple are visiting Bhutan as part of a week long visit to India and Bhutan that has taken in cities such as Mumbai, Delhi, Kaziranga, Bhutan and Agra.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge take part in a trek to the Tiger's Nest Monastery on the second day of a two day visit to Bhutan, April 15, 2016 in Paro, Bhutan.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge, pose next to a prayer wheel on the trek up to Tiger's Nest during a visit to Bhutan on the 15th April 2016 in Thimphu, Bhutan.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge start their hike to Paro Taktsang, the Tiger's Nest monastery, April 15, 2016, in Paro, Bhutan.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge pose with King Jigme Khesar Namgyel Wangchuck and Queen Jetsun Pem visit the Golden Throne Room of the Dzong, April 14, 2016 in Thimphu, Bhutan.

Prince William, Duke of Cambridge looks on as Catherine, Duchess of Cambridge fires an arrow during an Bhutanese archery demonstration, April 14, 2016, in Paro, Bhutan.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge arrive for a ceremonial welcome at Paro International Airport, April 14, 2016, in Paro, Bhutan.

Catherine, Duchess of Cambridge walks with HM Jetsun Pema Wangchuck in front of monks in the Tashichhodzong, April 14, 2016 in Paro, Bhutan.

Prince William, Duke of Cambridge walks with Catherine, Duchess of Cambridge as part of a ceremonial Chipdrel on arrival into the Tashichhodzong, April 14, 2016, in Paro, Bhutan.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge visit Pan Bari Village and walk through a tea garden at Kaziranga National Park, April 13, 2016 in Guwahati, India.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge visit the Kaziranga Discovery Centre built by Mark Shand's charity, Elephant Family, April 13, 2016, in Guwahati, India.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge ride a car during a Game drive at Kaziranga National Park at Kaziranga National Park, April 13, 2016, in Guwahati, India.

Catherine, Duchess of Cambridge visits the Centre for Wildlife Rehabilitation and Conservation at Kaziranga National Park, April 13, 2016, in Guwahati, India.

The Duke and Duchess of Cambridge watch dancers during the Bihu Festival celebration at the Diphlu River Lodge in Kaziranga National Park, Assam, India, during day three of the royal tour to India and Bhutan, April 12, 2016.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge meet Prime Minister of India Narenda Modi in New Delhi's Hyderabad House, April 12, 2016, in New Dehli, India.

Catherine, Duchess of Cambridge participates in an arts class with street children at a contact center run by the charity Salaam Baalak, which provides emergency help and long term support to homeless children at New Delhi railway station, April 12, 2016, in New Dehli, India.

Catherine, Duchess of Cambridge, visit the Salaam Baalak Trust, an organization supporting some of the most vulnerable young people living on the streets in Delhi, April 12, 2016.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge cut a birthday cake for Queen Elizabeth II at a Garden party celebrating the Queen's 90th birthday, April 11, 2016 in New Delhi.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge attend a birthday party for Queen Elizabeth II at the residence of the British High Commissioner, April 11, 2016, in Delhi.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge pay their respects at the place where Mahatma Gandhi's life ended on Jan. 30, 1948, at Gandhi Smriti, the Old Birla House museum, April 11, 2016 in New Delhi, India.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge visit Gandhi Smriti, a museum located in Old Birla House, where Mahatma Gandhi, India's founding father, spent the last few years of his life, April 11, 2016, in New Delhi.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge are seen at the India Gate during the royal visit to India and Bhutan, April 11th, 2016, in New Delhi.

Britain's Prince William drives a Formula E simulator at an event on young entrepreneurs in Mumbai, India, April 11, 2016. The Duke and Duchess of Cambridge are on a weeklong visit to India, their first royal tour in two years.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge place flowers at the Banganga Water Tank in Mumbai, India, April 10, 2016.

Catherine, Duchess Of Cambridge enjoys a game of cricket during a visit to meet children from Magic Bus, Childline and Doorstep, three non-governmental organizations, at Mumbai's iconic recreation ground, the Oval Maidan, during the royal visit to India and Bhutan, April 10, 2016, in Mumbai, India.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge visit the Banganga community April 10, 2016 in Mumbai, India.

The Duke and Duchess of Cambridge watch a game of cricket in Mumbais recreational ground, at the Oval Maiden, April 10, 2016.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge attend a Gala and reception with Bollywood stars and figures from the business world at the Taj Palace Hotel, April 10, 2016, in Mumbai, India.

Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge arrive for a Bollywood Inspired Charity Gala at the Taj Mahal Palace Hotel during the royal visit to India and Bhutan on April 10, 2016 in Mumbai, India.