Mark Mapletoft’s side demonstrated their ability to squeeze teams in that last four success, holding the Irish scoreless in the second half to win 31-20 after leading 22-20 at the interval.
The reigning age-grade Six Nations champions completed their Pool C campaign with a gruelling 17-12 win over South Africa last Tuesday at Athlone.
The World Rugby U20 Championship Pool C fixture on the Cape Flats had been deadlocked since the 51st-minute and the Exeter lock had been looking on from the moment three minutes later when his number was called and Olamide Sodeke was sent into the gruelling contest.
Repeated infringing from the Junior Boks, which included the yellow carding of Divan Fuller, meant the match continued level until its 86th minute.
The English were impressive 40-21 comeback winners over Argentina on opening day at the Championship last Saturday and coach Mark Mapletoft has decided to rotate his team for their second outing with skipper Finn Carnduff, Ollie Allan and Oli Spencer the three repeat picks.
It will be round three in Athlone on July 9 when that fancied duo – last year’s beaten semi-finalists – go head-to-head in an intriguing group that also contains a dangerous Argentina and a little known Fiji.
Coventry taught England U20s a valuable lesson as the club marked their 150th anniversary in style at Butts Park Arena.
The Irish closed out a hard-fought five-try, 36-0 win over Scotland in Cork, their last three tries coming in the closing 10 minutes, and it left England needing to beat world champions France in Pau to take the glory.
It was ahead of the round two match at home to Wales in Bath when Makepeace-Cubitt came in from the cold of English third-tier rugby to link up with an international squad made up of only Gallagher Premiership youngsters and the Racing 92-attached Junior Kpoku.