By Oliver Brett
BBC Sport, Port Elizabeth
Something happened in the fifth over of the World Cup semi-final which happens only once in a blue moon - an Australian batsman walked.
The Aussies had made a fast start and Sri Lanka captain Sanath Jayasuriya, with only three specialist bowlers at his disposal, had just turned to Aravinda de Silva.
Gilchrist had seen off Pulasthi Gunaratne, caning the seamer for two fours and a six and was looking in prime form when the 37-year-old De Silva entered the fray.
A specialist batsman who also bowls off-spin when needed, De Silva had been reasonably effective as a holding bowler in this World Cup.
But he had been clattered for 36 off just five overs when these two teams met in the Super Sixes.
Gilchrist was watchful to the first delivery before going down on one knee to the second and his attempted sweep lobbed up off bat and then pad.
Wicket-keeper Kumar Sangakkara trotted off towards short leg to claim the simplest of catches and the Sri Lankans celebrated a vital and unexpected success.
It seemed a good appeal. From the press box, at least, one sensed a double deviation before the catch was claimed.
But a pregnant pause followed as umpire Rudi Koertzen considered the decision and then began shaking his head.
The Sri Lankans began to look aggrieved before Gilchrist suddenly turned on his heels and marched off to the pavilion.
It was a stunning moment, if only because batsmen so seldom walk these days.
Australians, in particular, have a reputation for standing their ground even after offering the most blatant of edges.
They themselves are prone to admitting they only walk when the car breaks down.
In reality, they are no worse than the other Test-playing nations, with the exception of Bangladesh.
Gilchrist's decision to walk will have surprised his team-mates
The former South African bowler, Fanie de Villiers, watched the incident closely and in fact reckons Gilchrist did not really give himself out.
He said: "I was surprised about it. The edge was very obvious, you could actually see it go off the bat and then onto the pad.
"So Gilchrist would most probably not have expected the umpire to give him not out and when he looked up I think he missed the 'not' and only saw the umpire saying 'out'.
"That is why he walked off.
"It's very odd to see an Australian walk and Gilchrist may face a fine in the evening," he joked.
While Gilchrist will attract plenty of support and admiration from the game's traditionalists, Koertzen was made to look pretty silly by the whole situation.
After making one very poor decision in the New Zealand v Zimbabwe match, he was thought by some to be lucky to stand in a World Cup semi-final.
But locals in Port Elizabeth had always said he was likely to stand in the match. This is his home town.