England captain Michael Vaughan warned his side against complacency after their victory over South Africa on Tuesday, saying they had played "shoddy" cricket during some phases of the first Test.
"It's been common in England teams that when we get on top we've allowed South Africa back into the game," Vaughan told a news conference.
"Even in this game we had to have outstanding bowling and an outstanding catch to win."
England, who chased a target of 142, needed just 9.4 overs of the final day's play at Port Elizabeth to knock off the remaining 49 runs they required for a seven-wicket victory and their eighth win in succession.
But Vaughan had reservations.
"Every time this team has had questions asked of its character we have answered them in the proper manner," Vaughan said.
"But there were periods when we were shoddy, and that mustn't happen again."
Fast bowler Simon Jones had taken a spectacular catch to dismiss Jacques Kallis in South Africa's second innings on Monday and then claimed four for 39 as the home side lost their last five wickets for 28 runs.
"Simon is a dangerous threat when he gets the old ball, he gets reverse swing," Vaughan said.
"South Africa will come at us hard in Durban (where the second test starts on Sunday), and we will have to be up for the challenge."
Vaughan said England's greater collective experience had been an important element at Port Elizabeth.
"One of the key differences between the teams was the experience factor," he said.
"That first day when (Boeta) Dippenaar and (Jacques) Rudolph got in (for a stand of 102), they didn't get away from us.
"They allowed us to open the door and attack their inexperience, and that's exactly what we did."
Vaughan said the England record of eight wins in a row was a bonus.
"Going into the Test I wasn't thinking about it but now that we have created it, it is something special," he said.
