Watch it: Julius Francis, boxer-turned-security guard, decks unruly man

The power is the last thing to go.

Former heavyweight title contender Julius Francis and one-time opponent of Mike Tyson demonstrated that in his capacity as a security guard at the entertainment venue BOXPARK Wembley in London.

An angry man can be seen on a video that went viral yelling obscenities and scuffling with security staff and others.

The man then made the mistake of marching toward the 57-year-old Francis, who knocked him out cold with a vintage right hand about 45 seconds into the video.

Check it out:

Francis (23-24-1, 12 KOs) was stopped by Tyson in the second round in 2000. The Londoner, who last fought in 2006, also teaches children boxing and fitness