Agarwal, a self-made millionaire and founder of foreign exchange giant Rational FX, reiterated London mayor Sadiq Khan's commitment to ensure the city's voice is heard during Britain's negotiations with the European Union (EU) over an exit strategy.
"London was, is and will remain the greatest city in the world and best place to do business," he said at an event organised by the London Chamber of Commerce Asian Business Association in the House of Lords complex on Friday.
Agarwal, who was born in Indore and grew up in humble surroundings, said his new role was an opportunity to "serve London, which has served me so well".
"I arrived in this city in September 2001 with 200 pounds in my pocket. I did not know anybody but this city gave me all the opportunities. Now, it is my opportunity to make a difference," said the 39-year-old, who stepped down from his businesses to focus on his new role at City Hall in London last month.