Root stumped on 149 off a no-ball; also dropped on 16
Skipper shares in big stands with Moeen (61*) & Stokes (56)
Three wickets for Philander
England won toss; first of four-match series
Tom Fordyce
Chief sports writer at Lord's
Wonderful reception around Lord's for Root as that sweep shot raced away - the pitch may be a belter to bat on, but having arrived at 17-2 and seen his side listing at 74-4, his team-mates were not making it appear that way, and he has dragged them from the gutter to respectability.
Eng 224-5 (61 overs, Root 103, Moeen 14)
Moeen in the groove with successive dreamy cover drives to the boundary off Rabada which have the Lord's crowd purring. The batsmen have earned a drinks break.
Andrew Samson
BBC Test Match Special statistician
The last four England Test captains have scored a century in their first game as skipper: Andrew Strauss, Kevin Pietersen, Alastair Cook and now Joe Root.
There were a couple of reprieves for Root before he found his touch and recorded an important century for his team.
Vic Marks
Ex-England spinner on BBC Test Match Special
That's going to be a huge settler for him. Scoring runs makes it easier to captain.
No danger for the skipper this time, he sweeps the spinner, raises his bat and acknowledges the crowd. A great innings from the Yorkshireman, his 12th Test hundred.
Image source, ReutersRoot 99, Moeen 0
Another single for Root off Rabada and the captain will be on strike to Maharaj needing one more for his hundred.
Tms@bbc.co.uk
When Joe Root reached 75 in today's innings he exceeded the number of runs scored for England by Geoffrey Boycott (9166) in all forms of International cricket in 19 FEWER innings. Root in five years, Boycott in eighteen years!
Brian Burrows
Root 98, Moeen 0
Just the single to Root in this Maharaj over. Moeen making a watchful start, yet to get off the mark after eight deliveries.
Vic Marks
Ex-England spinner on BBC Test Match Special
It's been a fascinating day. South Africa took the first session, England won the afternoon and now this final session will decide the balance of the day.
Root 97, Moeen 0
Root collects consecutive boundaries with controlled edges wide of the slip cordon off Rabada. Just three away from a century on his first day of office.
#bbccricket
Theo Bowyer: Captaincy clearly not affecting Joe Root... another batting masterclass from England's lynchpin.
Root 88, Moeen 0
Maharaj drops short and Root rocks back to cut an assertive boundary. The England captain is still in his brilliant white chunky knit England sleeveless sweater, over a buttermilk, almost lemon coloured shirt that resembles ones my aunt brings over from America that used to belong to her late husband.
Image source, PAVic Marks
Ex-England spinner on BBC Test Match Special
I think we're going to see some short stuff to Moeen now. They'll sense they've got a chance now. 190-5 on this pitch is a good effort.
Stokes c De Kock b Rabada 56 (Eng 190-5)
South Africa have the breakthrough now though, Stokes has a dart at a short one and gets a glove on it down the legside through to the 'keeper. Not all that much batting left it has to be said after Moeen, who is in next. The partnership was 114.
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Sublime display from Root today, doing Sheffield and Yorkshire proud once again. Let's hope he can push on for the ton.
Alex R, Sheffield
Root 83, Stokes 56
The slow left-arm of Maharaj from the Pavilion End, the sun shining off his shaven head, which might provide a distraction for the batsmen. It would be more than the spinner is currently doing, one has to say, and Root records his 12th four with a deft sweep to the long-leg boundary.
We thought he had got there some time earlier, but, after some confusion over leg byes, here's the moment Ben Stokes officially reached his fifty.
Root 79, Stokes 56
Lord's still looking resplendent in the summer sunshine. A few have not made it back to their seats yet but the scene is sublime, no sign of those flying ants they had at Wimbledon - and also in the garden of the Walnut Tree public house yesterday afternoon. Two slips and a gully for the athletic Rabada and Stokes collects his eighth four with a back foot drive through the covers.
There goes the bell and the players will be stepping onto the hallowed turf any moment. England scored exactly 100 for no loss in that 27-over session so what would they be happy with at stumps? It's not going to be a prompt finish, we have 38 overs to get through, but we can continue until 18:30 BST and it is fairly certain we will. The light will not be a factor, that much we can say.