London: Kevin Pietersen marked his first Test innings against South Africa, the land of his birth, with a commanding 104 not out as England regained the initiative here at Lord's on Thursday.
England, at stumps on the first day of the first Test, were 309 for three, having been 117 for three not long after Pietersen came to the crease.
And England's position might have been worse had not South Africa missed a chance to run-out Pietersen before he'd scored.
But come the close they were on top, especially as South Africa captain Graeme Smith had decided to field after winning the toss in the opening match of this four-Test series.
Ian Bell initially led the fightback with some stylish shot-making before becoming more of a support act. However, at the close he was 75 not out, his unbroken stand with Pietersen worth 192 in 46 overs.
Despite a fine early burst from Dale Steyn and Makhaya Ntini, the Proteas' pace attack generally bowled too short before lunch.
The 28-year-old Pietersen, whose decision to turn his back on South Africa because he believed a racial quota selection policy was hampering his progress remains controversial in his homeland, found his form against left-arm spinner Paul Harris.
He drove him for four and lofted him down the ground for six off successive balls on his way to a fifty which he completed with a swept boundary off the slow bowler.
"What a day," said Pietersen. "Coming to the ground for my first Test against South Africa was very emotional and to walk off with 104, it's one of the most special days in my career.
"It was an amazing reception from the crowd. When I scored a hundred in South Africa, the crowd turned their back on me.
"But I've got nothing to prove. I love playing for England. I've been here for eight or nine years and everyone knows how passionate I am about winning games for England."
South Africa fast bowler Morne Morkel, who led the attack with two for 66 in 21 overs, added: "Maybe we tried a bit too hard but Kevin played an unbelievable knock."
Earlier, left-handed openers Andrew Strauss (44) and Alastair Cook (60) completed only their second century first-wicket stand in a Test match.
But, soon afterwards, South Africa, their quicks finding their range, took three wickets for three runs in eight minutes.
Strauss, born in Johannesburg, was lbw to Morkel before England captain Michael Vaughan was comprehensively beaten by an 88mph Steyn delivery and bowled for two.
Then five balls later, 117 for two became 117 for three when a short ball from the 6ft 6in Morkel proved too hot for Cook who spooned a gentle catch to AB de Villiers in the slips.
With England on the backfoot, Pietersen, off his second ball, ran a ludicrous single only for Ntini's throw from mid-on to miss the stumps with the batsman well short of his ground.
Steyn tried to shake Pietersen up by hitting him flush on the helmet with a bouncer. But, when he was set, Pietersen thrashed Steyn through the offside for four and confidently hooked a bouncer for another boundary.
Bell, under pressure for his place after making just 45 runs in four innings against New Zealand, and with Andrew Flintoff waiting in the wings, spent 43 balls in the 40s.
However, he completed an 89 ball fifty featuring five fours, all of which came in his first 24 runs.
Pietersen then raised the 150-stand with a typically extravagant whipped four through mid-wicket off all-rounder Jacques Kallis
Another swept boundary off Harris took Pietersen into the 90s.
South Africa took the new ball with England 276 for three off 81 overs.
But Pietersen's response was to clip Steyn off his legs for a four which got him to 96.
Then a forcing boundary shot through point off Morkel saw Pietersen to his century, which he celebrated flamboyantly by punching the air in delight as he leapt off the pitch.
He'd reached three figures in just 127 balls with one six and 13 fours. It was his 13th hundred in 40 Tests and his fourth at Lord's. But Pietersen's reaction spoke more eloquently than statistics ever could.