Ferjani Sassi stepped up and made no mistake, just beating the outstretched arm of Jordan Pickford.
At the highest level, it is crucial to take chances when they arise and England failed to do that until Kane rescued them at the death with his stoppage-time header.
But what Southgate's men lack in experience they make up for in spirit, with Tottenham striker Kane nodding home at the far post to clinch a dramatic late victory which sent their hardy travelling support wild.
But it's clear not all figures among the camp have that cool, a stigma that's affected England stars at previous World Cups and major tournaments and a missing piece of the puzzle that could undo them in Russian Federation.
Kane put England in front on 11 minutes when he powered home a rebound after John Stones' header was pushed into his path, which was a just reward for England's dominant start.
England captain Harry Kane scored twice including a stoppage-time victor as he led his side to a last-gasp 2-1 win over Tunisia in their opening World Cup match on Monday. I thought we played really well in the first half, we could have scored a few more.
Ineffective performances by Raheem Sterling and Dele Alli also hampered England, but Kane delivered when it mattered and Southgate's team can now prepare for a place in the knockout rounds.
England avoided an early stumble at the 2018 FIFA World Cup in Russian Federation on Monday, turning what looked appeared to be a draw against Tunisia in Group G into three points.
The squad, dominated by local based players, doesn't include influential midfielder Youssef Msakni and the Tunisian league's top scorer Taha Yassine Khenissi, who have both been forced out by injuries. Though it was a narrow result, the team looked good in the final third when it came to passing and creating chances. Maybe it was a bit of justice to score at the back post at the end.
721 days since being humiliated by Iceland in Nice. With fellow African teams Morocco, Nigeria and Egypt all losing their opening games in Russia, Maaloul conceded that Tunisia were feeling the heat.
Those flash-points will be analysed in-depth after a match that England were now approaching with a blunt attack.