It has to be one, which you’ve actually seen, and almost certainly live. A batting exhibition, which made you feel different about the player, the game in general and about the bounds of what was possible. To rethink everything you had thought before. The context and consequences of the innings are also significant.

Graeme Smith did it with his unbeaten 154 to beat England and win the series at Edgbaston in 2008. He had many others, but that was his ‘other-world’ moment. Jacques Kallis scored a hundred in both innings against India on a dry, turning pitch at Newlands against Harbhajan Singh when he decided that the reverse-sweep was necessary despite rarely having practised it, never mind employing it in a Test match with the series at stake.

AB de Villiers scored 150 when walking to the crease with 12 overs remaining in an ODI against the West Indies at the Wanderers – that most definitely redefined the boundaries of possibility. But for all his brilliance, the most astonishing Test innings he played was against Australia on the last day in Adelaide when he scored 33 off 220 balls without a boundary to save the game. That truly redefined the way many people viewed a game they thought they had known all their lives.

That was the Test match before Hashim Amla played the innings which springs first to my mind when reflecting on an international career that included a very great number of highlights.

South Africa had escaped with a draw from a potentially desperate situation in Brisbane thanks to a Kallis century and a day of rain. Michael Clarke scored a bruising double century. He scored another one at the Adelaide Oval but it proved in vain, again, as debutant Faf du Plessis made a century while de Villiers blocked the life out of Australia’s attack for five hours on that astonishing final day.

When the teams arrived for the decider at the WACA ground in Perth, both were supremely confident. The Australians had authentic and conventional reasons for being so. The Proteas convinced themselves that, having weathered the storm, the forecast would change. There was little practical evidence to suggest it would.

Indeed, having batted first on a Perth ‘belter’ the tourists were 75-6 just before lunch. Even when du Plessis (78) added 50-partnerships with Robbie Peterson and Vernon Philander to haul the total to 225, it seemed a long way below par. But then Dale Steyn (4-40) did what he used to do and Australia were 45-6 before recovering to 163 all out, an unexpected but not fatal deficit of 62. It had been an eventful Test match, but it was only just beginning.

Amla and Smith eviscerated Australia’s attack in the second innings, an onslaught that was literally eye-watering to watch. They added 178 together in just over 25 overs. Think about that – and what was at stake. Clarke and the Australians were bullishly certain that there would be no repeat of the first ever South African series win on Australian soil following the triumph four years earlier and the captain had the services of his two scowling left-arm Mitchells to make sure it didn’t happen, Johnson and Starc.

Amla became a surgeon in an abattoir while Smith chopped and hacked like a brutal butcher. It was hard to control breathing describing it. It looked like the two batsmen were trying to keep up and even outdo each other, and that’s because they were. “We went a bit berserk out there, it was all I could do to keep up with Hash, but he was in a different class,” Smith said several days after victory had been secured.

The Mitchells lost their collective rag and made their feelings known. Smith enjoyed it, Amla appeared not to notice. He flicked perfectly fine deliveries from outside off stump and cut rib-high lifters through point. He made excellent bowling look ordinary until it actually became ordinary. He rendered the Mitchells impotent and silent. Only when Smith departed for 84 did he awake from the hypnotic spell that he had been cast under, or cast upon himself.

By the end of the second day he was 99 not out. Early on the third morning he reached his century from just 87 balls. AB de Villiers walked out to bat at 287-3. Amla took a back seat but continued to collect boundaries as though selecting the best fruit from a tree. To the casual and even professional observer there was little correlation between the merit of a delivery and its outcome. It was truly a time to re-evaluate the art of batting.

Amla added another 149 with De Villiers (169 from 184 balls) before finally departing for 196 from 221 deliveries. Steyn led from the front once again to bowl Australia out for 322 and defeat by 309 runs.

Numbers are just that. They will always be there, can’t deny them. Emotions are harder to record. Amla and Smith brought up their 150 partnership from 116 deliveries, the highest strike rate ever in Test cricket for a partnership that size. And Amla, the man renown and lauded for his kind, gentle and empathetic demeanour, had been anything but at the crease. Great memories.  Go well, great man.