A little known fact that the late, great James Brown averted a riot following the 1968 assassination of Dr. Martin Luther King Jr. is the foundation of a new film, which gets its European premiere in London on June 16.

"The Night James Brown Saved Boston" will be screened as part of the June 14-22 Meltdown Festival, being curated at London's South Bank Centre by U.K. electronic act and trip-hop pioneers Massive Attack.

Released to coincide with the 40th anniversary of the civil rights leader's death, the 90-minute documentary by awarding-winning U.S. producer David Leaf features rare footage of Brown's performance at the Boston Garden just 24 hours after the assassination.

Most major U.S. cities were torn apart as angered African-Americans rioted in response to the violent loss of their influential leader. Boston, however, remained calm as the city's citizens stayed at home to watch Brown's mesmerizing live-TV performance, during which Brown pleaded with locals not to respond with violence. Almost 25 minutes of the TV show, never seen outside Boston since that original 1968 transmission, has been added to other archival material for the film project.

"What we're looking at is one of the worst weeks in the 20th century and one of the worst episodes of civil unrest in the country," Leaf tells Billboard.biz. "We're also reminded of what a vivid performer and dominant stage presence James Brown was. There would have been no Michael Jackson, no Mick Jagger, no Prince without James Brown."

The U.S. premiere of "The Night James Brown Saved Boston" took place at South By SouthWest in March. The DVD edition will be distributed by Shout! Factory in the U.S. from August. International distribution will be handled by the U.K.'s FremantleMedia Enterprises.