Fourth Test, Johannesburg:
England 180 v South Africa 215-2 (day two, stumps)
Play resumes Saturday: 0800 GMT
Coverage: Test Match Special on BBC Radio Four Longwave, Radio 5 live sports extra, Red Button and BBC Sport website; text commentary online and on mobiles. Also live on Sky Sports
Smith's second successive ton is likely to have a key impact on the series
Graeme Smith's controversial century helped South Africa take a 35-run lead over England at 215-2 on a weather-hit second day in the final Test.
England were convinced Smith had edged behind when on 15 and referred the not out decision to the third umpire.
However, Daryl Harper did not have his speaker level up high enough to hear any noise on the television replays and Smith was able to continue his innings.
The skipper went on to score 105 and share 165 with Hashim Amla (71).
Play somehow resumed after a torrential storm but just 23 balls were bowled before bad light ended proceedings.
Having capitulated to 180 all out on the opening day, England, who lead the four-match series 1-0, knew their hopes of salvaging the match and securing their second successive series win in South Africa rested on a successful morning session.
It was Smith's sixth century against England and his 20th in Tests but, superbly constructed innings though it was, it will be the controversial referral system that is remembered in connection with it.
And once again the controversy surrounded the much-criticised Harper, even when he was in the comparative calm of the TV umpire's room.
England were certain Smith had edged a Ryan Sidebottom delivery to Matt Prior but umpire Tony Hill turned down the vociferous appeal.
The bewildered tourists immediately asked for the decision to be referred and a clear snick was heard on the replays.
However, Harper insisted he did not hear any noise, and an investigation soon discovered that he did not have the sound turned up to its maximum level.
In any case Harper informed umpire Hill that there was no obvious reason to change the verdict and Smith was able to continue his vital innings.
Why the New Zealander had not heard the edge himself from 22 yards away is perhaps equally mysterious.
In the next over Stuart Broad induced an edge from Ashwell Prince that was beyond any doubt whatsoever and Graeme Swann safely pouched the chance at second slip.
However, an improved England performance with the ball could not prevent a pivotal sixth century partnership between Smith and Amla, all of which have been in excess of 150.
It was a surprise to see Broad open proceedings instead of the more clinical James Anderson but the Nottinghamshire seamer produced a fine spell.
Broad found pace and carry with good accuracy, but the crucial element of luck eluded him and the fifty stand was reached from 81 balls with successive drives for four, which prompted the introduction of spin.
Swann immediately caused problems for Smith with some sharp turn and bounce but the skipper recorded his fifty from 104 balls when Broad strayed on to his pads.
No sound from Smith's bat was heard by the umpires on or off the field
Smith mowed a delivery from Swann in ungainly fashion to bring up the century stand and Amla also recorded his fifty with a four - his sixth - when Alastair Cook dived clumsily over the ball at cover and rather summed up the mood of English despair as the South Africans reached lunch only 20 behind.
England began the afternoon session in fighting style, Broad peppering Amla with a succession of short-pitched deliveries, often from round the wicket.
The batsmen continued to ride their luck on occasions, particularly Amla, with edges falling agonisingly into gaps in the field.
Finally, after an away swinger from Sidebottom, one went to hand to end the 41-over partnership as England skipper Andrew Strauss took a safe catch at first slip.
The combative Sidebottom, in his first Test since February, was celebrating his 32nd birthday but his evening meal will be soured somewhat by the thought that Smith might have scored 90 more runs than he merited.
The formidable presence of Jacques Kallis was hardly a reassuring sight for the tourists, but the darkening skies were.
Soon a momentous clap of thunder followed, the heavens opened and the ground was completely waterlogged in a matter of minutes.
Many a ground would have been unplayable, probably for the next day as well, but a combination of free-draining Johannesburg soil and hard-working groundstaff allowed the match to resume in watery late afternoon sunshine.
England might have sensed an opportunity to utilise any moisture in the surface but the resumption proved uneventful as seven runs were added before the umpires decided that it was too dark.