London - England debutant Tom Westley's fifty saw the hosts remain in charge of the third Test against South Africa at The Oval on Sunday.
England were 153 for two in their second innings, already a lead of 331 runs, at lunch on the fourth day of what is the 100th Test staged at The Oval.
Number three Westley was 50 not out following his first-innings 25.
Meanwhile, England captain Joe Root was 38 not out, having so far helped Westley add an unbroken 61 for the third wicket.
South Africa's lone success in the session saw them dismiss opener Keaton Jennings.
But the rain that started to fall during the lunch break suggested that novice skipper Root might have to declare earlier than he would like if he wants to give his bowlers enough time to force a win that would put England an unbeatable 2-1 up in this four-match series with just one to play.
England resumed on 74 for one, a lead of 252, with Jennings 34 not out and Westley 28 not out.
South Africa-born and raised Jennings -- England-qualified through his mother and residence -- had launched his Test career with a century on debut against India in Mumbai in December.
But a duck on the first day of this match meant the Durham left-handed opener was under pressure for his place, having reached double figures just once in his last five innings.
Jennings had battled hard for 48 when he was caught in the gully after fending at a lifting ball from fast bowler Kagiso Rabada.
It was the end of a 115-minute innings that featured 78 balls including nine fours and a stand of 62 with Westley that had taken England to 92 for two.
Westley, one of three debutants in England's XI, demonstrated many of the grafting qualities critics of the team's top-order had said they lacked during a massive 340-run defeat in the second Test at Trent Bridge.
The Essex right-hander added just nine runs in Sunday's first hour -- although he did clip a full length ball on off stump from Rabada wide of mid-on for a well-timed four.
And when Vernon Philander, who spent the second night of this match on a hospital drip with a viral complaint, dropped short outside off stump, Westley eased him behind point for another elegant boundary.
The seamer did go past Westley's outside edge several times, however, as did Morne Morkel.
But the composed Westley clipped fast bowler Morkel off his pads for a boundary that saw him to a 119-ball fifty, including nine fours.
England established a strong position in this match with a first-innings total of 353 built on Ben Stokes's 112 and former captain Alastair Cook's painstaking 88.
Pace bowler Toby Roland-Jones, another of England's debutants, then took five for 57 as South Africa were skittled out for just 175 in reply.