In the end Walsh prevailed, beating reigning world champion Kovacs into second place and leaving title favourite Crouser without a medal.
With the protests done and dusted, the Americans praised the efforts of their downunder opponent. Crouser, previously unbeaten this year, agreed that Walsh "earned it. He threw really well and was consistently at the top of the field."
Kovacs, the Rio silver medallist, remarked: "I wanted the gold but my hat's off to Tom Walsh with some great throwing."
Walsh said he was proud of his achievement, which goes with the world indoor gold medal he won in Portland last year and the bronze he picked up in Rio. Once an apprentice carpenter, Walsh is now a very part-time builder and full-time athlete. He spends his life training, travelling and competing.
His win was worth $82,000 but his new status as world champion is sure to open some commercial doors. His coach Dale Stevenson expects more opportunities will come Walsh's way.
Before the London contest, Walsh declared he felt confident going up against his big-name rivals. He didn't even allow a groin strain, picked up in training a couple of days before competition, to throw him off his stride, saying he did not want to use the injury as an excuse.
His parents say their powerful son has loads of self-belief. Peter, Walsh's father, national junior men's shot put winner in 1964-65, said his son "knows he can win and doesn't doubt himself".
Walsh's triumph moves him into contention for a top New Zealand sporting prize to go with his London medal. The Halberg Awards honour our highest achievers in sport, and among the men Walsh and America's Cup skipper Peter Burling would so far be the year's leading contenders.
After his heroics at the Olympic Stadium, Walsh planned a night out with family and friends. He wanted to find a pub and enjoy "a few pints and a burger or steak". The 120kg star athlete was feeling "pretty toey for a feed". He deserved a treat.