"I don't think we could have picked a better location," Rumble added.
Nutter finished off the crowd with a passionate pitch for the city and his role.
"We are a service company," he said of his administration. "My responsibility is to bring value and return on investment for my 1.5 million shareholders."
His audience was about 60 business executives attending a British government-sponsored workshop on doing business in the United States. From the intense applause, it was clear Nutter had not been speaking to his City Council.
"Very inspirational," was the reaction of Ben Brocklesby, sales director for Origin Frames Ltd., a manufacturer of aluminum doors and window frames. "He is clearly passionate and insightful when it comes to his city."
The event was part of a busy first full day of Nutter's eight-day trade mission to London and Tel Aviv. It followed a visit to the U.S. Embassy, a briefing on the United Kingdom's economy, a private meeting with Prince Edward, and tours of the House of Parliament and Big Ben.
The first day included Nutter being able to announce that the 2015 tour of the Philadelphia Orchestra will include two days in London.
The workshop, however, was the purest expression of the trip's intent - to convince foreign firms to think of Philadelphia when expanding overseas.
Nutter could have found no better partner than Rumble, who described being taken first by Nutter's pledge to make Philadelphia the No. 1 "green city" in America and then by the intimate relationship the Mark Group built with the administration.
"Michael Nutter told us he was not interested in a transaction," Rumble said. "He was interested in a relationship, and that is what it has become."
Nutter took questions from the group, winning them over as much with his dry humor as his pitch.
When one business owner noted he had opened his U.S. headquarters in Sarasota, Fla., Nutter gave him a blank stare.
"Never heard of it," the mayor said.
He drew laughter again when he argued one selling point of Philadelphia was its proximity to "our northern suburb . . . New York."
David Brown is chief executive officer of a firm that provides interpersonal skill coaching using live performances to show the hows and how-nots.
"Look around. He is the only mayor in the room," Brown said. "That makes a difference."