Bill Bratton: 'I Never Close Any Door Before It's Opened'

— -- At 63, Bill Bratton, the former top cop in Boston, Los Angeles and New York City, has a career of high caliber police work behind him, but there's one job he hasn't closed the door on: leading Scotland Yard.

"I never close any door before it's opened," Bratton told ABC News' David Muir.

British Prime Minister David Cameron, who offered Bratton a job on Friday, initially wanted him to serve as commissioner. The move was overruled by Home Secretary Theresa May, who said only a British citizen should hold the position.

Bratton will instead serve as a consultant to the police force.

"If it had been open, I certainly would have looked with great interest at possibly applying," Bratton said of the top job.

The London Metropolitan Police commissioner is not responsible just for the police force in London, but also for national security.

Bratton compared it to the New York City police commissioner also leading the FBI.

"It is the most prestigious, most complex, and at this time most challenging police leadership position in the world," he said.

British police have been criticized for struggling to contain an outbreak of rioting that began in London last week and spead to other cities.

Looting, fires and violence raged in the streets as people protested the fatal police shooting of Mark Duggan, a 29-year-old black man.

It was four days before police got a firm handle on the situation.

In all, five people died and more than two thousand people were arrested.

The riots were riddled with racial tensions and class warfare, something Bratton dealt with firsthand in Los Angeles.

"Race, ethnic and cultural issues -- those are phenomenal challenges they're going to have to face," he said.

Bratton called his time in Los Angeles the most worthwhile seven years of his life.

After the rioting, it became clear to Cameron that Bratton would be the right man to help curb gang violence and racial tensions in Britain.

"I believe we should be looking beyond our shores to learn the lesson from others who have faced similar problems," Cameron said.

Bratton will leave for London at the end of August. He's looking forward to making a positive impact in his new role. As for the commissioner of Scotland Yard?

"Whoever gets into that position has an incredibly difficult job ahead of them," he said.

ABC News' Richard Esposito contributed to this report