The 39-year-old -- whose previous best was silver in the 2007 world championships -- was even able to enjoy his version of the royal wave down The Mall leading from Buckingham Palace after leaving his rivals trailing from an early stage of the gruelling event.
Diniz spent so much time celebrating with spectators close to the finish that he missed the opportunity to eclipse his own world best mark as he finished in 3hrs 33min 12sec, 39sec short of his mark from Zurich in 2014 when he won the third of three European titles, but still the second fastest time in history and a championship record.
It was a far happier outcome than his experience in the 2012 Olympics where he was disqualified before being captured disconsolately leaning on a tree in The Mall, or last year's Rio Games where he collapsed twice before bravely finishing eighth.
However, Diniz -- who was also disqualified in the 2008 Olympics -- confessed to having to pull himself together at one point when he received a warning.
"I started having doubts after 20km," said Diniz.
"I got a card around 20km too and I thought, 'I just must not mess this up'. I just concentrated completely on my technique."
Diniz, who gave France their third gold medal of the championships, said he had purposely avoided watching Saturday's action.
"A lot of training has gone into this –- cycling, swimming –- everything for this 50km walk. Last night I kept away from watching the TV (athletics) because I did not want to get too excited. I went to bed at 9pm because I knew it was going to be my day today."
Despite his advancing years, Diniz said he was likely to carry on and have one last tilt at winning the only major title that has eluded him -- the Olympic gold.
"It is a lovely Sunday afternoon. I know you should never take any decision when you are hot," he said.
"I am still missing one (title) and that is the Olympic one. It would be a nice way to finish in Tokyo."
Japan's Hirooki Arai came second -- giving Asia their highest ever placing in the event -- and team-mate Kai Kobayashi took bronze, finishing eight minutes in arrears of the winner.
The women's race made its debut at the championships -- with just seven competitors -- and was won by Ines Henriques of Portugal breaking her own world record, timing 4hr 05min 56sec.