England's winning streak in Twenty20 cricket came to a dramatic end on Friday as South Africa squeezed home off the final ball to claim a three-wicket victory at Newlands.
Eoin Morgan's men were unbeaten in the shortest format in 2015 and appeared set to defend a modest total of 134-8 when South Africa began the final over of the reply 15 runs short of their target.
However, Chris Morris - the Proteas' batting hero in last week's fourth one-day international between the sides at Johannesburg - smashed successive boundaries off Reece Topley to keep his side in the hunt.
And South Africa duly prevailed in thrilling circumstances as, with two still required from the final ball, Topley failed to cleanly collect Joe Root's throw from long-off when the bowler had the opportunity to run out Kyle Abbott at the non-striker's end and force a tie.
Morris finished unbeaten on 17 from seven balls, while Imran Tahir could also take significant credit for South Africa's win, which puts them 1-0 up in a two-match series, after returning 4-21.
Alex Hales (27) and Jason Roy (15) took the tourists to 36 without loss after three overs, but the dismissal of the latter - to a mis-timed pull off a Kagiso Rabada slower ball - triggered an alarming slump.
Tahir claimed four of the next five wickets to fall as England slipped from 52-1 to 81-6 - his first scalp coming when JP Duminy somehow completed a fine catch in the deep to dismiss Hales, despite being clattered by a diving Rabada just after taking a steepling chance.
After Tahir had come within a whisker of completing a hat-trick, a googly almost bowling Chris Jordan, England were grateful for an unbeaten 32 from Jos Buttler.
Although Buttler then offered Hashim Amla an early reprieve in the reply, South Africa were unable to take command of proceedings, wickets again falling on a regular basis as Ben Stokes (1-19) and Jordan (3-23) excelled.
When Jordan removed David Miller (13) and David Wiese (2) in the 19th over, while giving up just six runs, the pendulum appeared to have tipped decisively in England's favour.
However, Morris reprised his batting heroics from a week earlier, crashing Topley for back-to-back boundaries before scrambling successive twos to finish the job.