The majestic David Rudisha retained his Olympic 800 metre title with another middle-distance masterclass on Monday.
Rudisha smashed the world record to take gold in London four years ago and proved he is still the fastest man in the world over two laps in Rio.
The elegant Kenyan was a class apart once again, clocking a season's best of one minute and 42.15 seconds to win in style ahead of Taoufik Makhloufi of Algeria and America's Clayton Murphy.
Alfred Kipketer set a blistering early pace from the gun, but the teenager was never going to be able to keep it up.
Kipketer's compatriot Rudisha reeled him in for a second time soon after the bell and the 27-year-old took control down the back straight and his rivals were only able to catch him.
The two-time world champion kicked for home, striding away with easy in another bravura performance on the big stage to become the first man since Peter Snell back in 1964 to successfully defend his Olympic 800 title.