Quinton de Kock dedicated his sixth Test century, and highest score in the format, to a friend who lost his finger in Afghanistan and to rhino conservation in South Africa. de Kock celebrated both his fifty and his hundred by holding his bat lengthwise to show the name of Rockwood, an organisation fighting to save the endangered rhino, and made a hand gesture, holding the ring finger of his right hand down with his thumb and spreading the other three fingers.

"It's just a friend group I have back home," de Kock told the host broadcaster. "A couple people know I am doing this initiative with the rhino thing and one of my friends got his fingers shot off in Afghanistan, and I said I will salute to him."

Later, he told the press conference a little more. "I am doing Rockwood and the Rhino conservation and it's a whole group of us. The one night we had a braai and we started talking and I said his finger being shot off is quite a limelight in our group of friends so I said I will do that as an accolade for him. I couldn't believe it happened first time. I am sure my phone with the boys' group is going to be buzzing."

de Kock seemed in lighter spirits than he had throughout the 2020-21 summer, when he was asked to captain South Africa in all three formats moving between bio-bubbles. He finished the season after being given time off for the domestic T20 tournament, which the South African Cricketers' Association described as a mental health break. de Kock explained that it was the restricted environment, not the leadership, that necessitated his time off.

"It didn't have anything to do with the captaincy. It had to do with the Covid bubbles. Being under so many bubbles took its toll. It was just too much," he said. " I asked for a break; if I can just relax for the T20 series back home and they deemed it a mental [health] break. I wasn't mentally tired, from cricket at least. I was just tired from bubbles. I had enough of them."

He described South Africa's trip to Pakistan in January-February as particularly difficult, as it came after several other tours and was the most strict of the lot. "We were on the road right from the IPL, but being in the Pakistan bubble was particularly difficult, especially just going from cricket change room to one floor of rooms. That's how we stayed. No balconies, no nothing, no room to move. I just asked if I could have a break. Ever since then, it's been good."

Since then, de Kock scored one half-century for the Mumbai Indians in the IPL and had two scores above 35 before the tournament was postponed. He returned to international form with his century in the Caribbean, his first Test score over 30 in seven innings to break a lean patch that was starting to get under his skin. "If I was getting starts and wasn't converting that would have irritated me more but during this last while I wasn't even getting starts," he said. "Now, for me just to bat through, is great."

He assessed conditions in St Lucia as offering plenty of movement but also reward for those willing to dig in. "It was difficult. Even in the 75th over, it was still swinging a lot. Obviously there is still a lot in that wicket. If you bat right, there could be an opportunity to score runs and if you bowl well there is also an opportunity to take wickets. It's been a fair contest so far."

But with South Africa having their noses far in front, de Kock expected the match to end with time to spare. "If we had to just keep doing what we're doing, building pressure, we should have the game closed by tomorrow," he said. "In saying that, they've still got some good players to come. We've seen this team bat deep before."

Should South Africa manage that, it may mean no more gestures from de Kock for his friend or the rhinos in this match. Asked to explain his decision not to participate in any anti-racism gestures at the start of the Test, de Kock said. "My reason - I will keep it to myself. It's my own personal opinion. Like Lungi [Ngidi] said, it's everyone's decision. No one is forced to do anything. Not in life. That's the way I see things. That's just about it."

After adopting a collective stance not to take a knee last year, South Africa gave their players a choice in the Caribbean. Six of the playing XI and the entire support staff took a knee and four raised their right fists while standing.

Firdose Moonda is ESPNcricinfo's South Africa correspondent