Finn struck three times in seven balls yesterday morning, after James Anderson had administered the first blow with the wicket of South Africa captain Graeme Smith. The pace bowlers ended the day with three wickets each.
But from 54-4, South Africa dug in to make up for early losses on a predictably even surface to close on 262-7, thanks in large part to Duminy (61) and Vernon Philander.
England need victory here to share the series and stop their opponents knocking them off the top of the International Cricket Council world rankings.
They could hardly have hoped for any better in the first session, after Smith – setting a new world record here, as captain for the 94th time in a Test – chose to bat first under cloud cover.
He soon knew he and his opening partner Alviro Petersen would be in for an examination of technique and judgment as England’s pace bowlers found movement in the air, and a little off the seam.
It was not until Anderson opted for a new line of attack against Smith that England got their breakthrough, though.
Anderson went round the wicket from the pavilion end, and pushed one further up and wide. Smith followed it down the hill – and although his bat hit the floor as well as the ball, umpire Kumar Dharmasena’s initial not-out verdict for caught-behind had to be overturned when England requested DRS.
Smith’s early exit was an evident relief for the hosts, at a ground where he has made a double-century and another hundred too from three previous Test innings.
Much more was required, though, while overhead conditions continued to favour the bowlers – and Finn did not disappoint on his home ground, having been chosen ahead of Yorkshire’s Tim Bresnan.
First a little extra bounce undid Petersen, who gloved a catch behind down the leg side. He took his bottom hand off the handle almost at the moment of impact, but not obviously enough for there to be serious doubt about the validity of the decision.
Jacques Kallis was off the mark with a leg-side single first ball, putting No 3 Hashim Amla back on strike, where he was to depart to a very good delivery, bowled between bat and pad by Finn.
England’s 6ft 8ins seamer was not finished either.
He took his third wicket for just three runs when lynchpin Kallis became the second batsman to go caught-behind to him down the leg side.
This time it seemed, after England again reviewed Dharmasena’s initial not-out verdict, that – in a near action-reply of Petersen’s dismissal – the bottom glove might well have been off the handle when it was hit.
But after much deliberation, and to the obvious dismay and disbelief of Smith and others on the South African balcony, third umpire Rod Tucker ruled otherwise.
After a delayed start to the afternoon session, because of a lunchtime shower, England were on the other end of the next DRS ruling when Hawkeye could not overturn an lbw reprieve for AB de Villiers off Anderson, the decision standing on the grounds that impact with pad was too close to being outside off stump.
It cost England their remaining review, but no runs – Anderson concluding a sequence of 13 dot balls to De Villiers with his wicket, well caught by Alastair Cook away to his left at third slip, to end a stand of 51 with Rudolph.
The latter continued the fightback in the second of three consecutive half-century stands, alongside Duminy, until the left-handed alliance for the sixth wicket was broken soon after tea when Rudolph edged onto his stumps as he tried to work Graeme Swann to leg.
That gave the off-spinner his first Test wicket in 92 overs, dating back to Trent Bridge at the end of May against the West Indies.
If England were planning a surge to wrap up the tail, Duminy and Philander saw to it that no such thing happened.
Philander rode his luck, especially against the short ball, on his way well past his previous career-best 29 to 46 not out, and Duminy, who has had his struggles in the past against Swann in particular, kept out 157 balls.
His six boundaries were hard-earned, and it was not until Anderson returned with the second new ball that Duminy reached out at a wider delivery on the back foot and got a bottom edge to give Matt Prior his fourth catch of the day.
The highest stand of the innings, worth 72, had nonetheless restricted England’s advantage, and a power cut took out two banks of floodlights to help bring an early close as the clouds rolled in again.
Finn believes England proved their character after a troubled week.
Asked if it was good to finally play after the controversy of the week, Finn said: “Yeah. We’re 11 guys who just want to go out and play.
“After Monday everything was swept under the carpet. We’ve got through tough times together, we’ve done that well in the past and we showed that again.
“We bowled well. We bowled in partnerships well. They aren’t away from us – they only scored at three an over. It would have been nice (to bowl South Africa out) but it is good that we stuck to our guns.”