Stuart Lancaster has warned England they have to play for 80 minutes if they are going to win the test series against Argentina 2-0.
England ran in four tries as they beat Argentina 32-3 in the first test in Salta, but faded in the second half when they only scored seven points.
Winger David Strettle, centre Billy Twelvetrees and back rower Ben Morgan touched down in the first half as England led 25-3 at the break before Billy Vunipola finished it off with a try in the last minute.
Lancaster said: "In the first half, we were accurate and we played with an intensity and pace that Argentina struggled to match, but we need to improve our second half going into the next match."
Captain Tom Wood added: "The players realised we had to start well, so we upped the intensity of our warm-up. But Argentina came out firing in the second half, so credit to them and that is a huge wake-up call."
The win sets up the chance for Lancaster's men to make history in Buenos Aires this week as no England side have won a series in Argentina 2-0.
Bill Beaumont's side came closest, winning one and drawing one in 1981, but England will be firm favourites in the second test after dominating most of this match.
Meanwhile, hosts South Africa beat Italy 44-10 and Samoa defeated Scotland 27-17 in the opening round of a four-team tournament in Durban.
Adriaan Strauss, J.J. Engelbrecht, Bryan Habana, Jean de Villiers and Bjorn Basson scored tries in South Africa's rout, while Alesana Tuilagi touched down twice as Samoa beat Scotland for the first time in nine meetings.
Samoa meet Italy and South Africa play Scotland in the second round of games on Saturday.
Agence France-Presse, Associated Press