The 30-year-old opening batsman is in charge for the series opener after regular test captain Faf du Plessis decided to remain at home with his wife following the recent birth of their first child.
Du Plessis is, however, expected back in time for this month's second of a four-test series at Trent Bridge.
In the meantime it falls to Elgar to lead the side at the 'home of cricket', where the Proteas have not lost in six tests since their re-admission to international cricket, a sequence comprising four wins and two draws.
Elgar, asked at a Lord's news conference on Wednesday how he would feel walking out onto the ground on Thursday, replied by saying it would be the "most proud day so far of my career".
He added: “Everything about Lord’s seems to want you to do better. You hear all the folklore when you’re growing up and you watch it on TV, and it always looks so nice.
"Once you reach the big arena all those memories come flooding back, and you have your first opportunity to play here and try do well here.
"It's an enhanced feeling when you get here, an emotion to try and do well. That’s the feeling anywhere in the world," explained Elgar, who has scored seven hundreds in his 35 tests, with a career batting average of nearly 40.
"But because Lord’s has got so much tradition and history it’s maybe a little bit more than other venues."
Elgar stressed that all that had to be put to one side come the match itself, saying: "As a captain you have to look at it as another game of cricket.
"You can't let the occasion get the better of you. Give it the acknowledgement and respect like it does deserve, but you’ve still got a job to do."
- 'Clown' -Meanwhile Elgar had no doubt he would be able to exert all the authority he required, even though he's set to be in charge for just the one test.
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