Prince William and his wife Kate met Boman Kohinoor, owner of a famous Mumbai Parsi cafe, on Sunday at the city's Taj Mahal Palace hotel.
The royal rendezvous took place after they were told of the campaign with the misspelled hashtag #WillKatMeetMe.
Mr Kohinoor has a strong claim to be India's oldest and biggest royalist.
The huge cardboard cut-outs of William and Kate that adorn his restaurant reflect a lifetime of devotion. In 2010, he wrote to the Queen asking her to visit and she replied to thank him on a letterhead stamped with the Windsor crest.
In pictures: Day one of the royal tour
"I met Their Royal Highnesses [on Sunday] evening at the Taj," Mr Kohinoor told Conde Nast Traveller.
"They were very kind and asked me about my restaurant and my favourite dishes there.
"I told them about the berry pulao and how it's made using my late wife's recipe."
Mr Kohinoor said that he was asked by the royal pair if he could cook. "I said no, but I serve my customers well," he replied.
"I told them: Give my love to the Queen, and to [your] children Prince George and Princess Charlotte, too.
"I wish I had more time to speak, but I'm thankful for this opportunity."
The veteran restaurateur said that he was given the opportunity after a video in which he pleaded to meet the royal pair was posted on the internet.
"TRH (their royal highnesses) were very touched and invited him to their hotel before last night's charity gala," Kensington Palace tweeted on Monday,
Earlier at the Taj Mahal Palace, the couple spoke to survivors of the 2008 terror attacks in the city.
The seven-day tour will also see them travel to the remote Himalayan kingdom of Bhutan.
The dream of a 93-year-old Indian restaurateur to meet the Duke and Duchess of Cambridge has come true after a viral social media campaign.