We have waited for England to click in this tournament. This win was not perfect but it was undoubtedly their best of the tournament so far.
Jacks is in the middle of the best form of his career – a run that gives England serious threat.
His runs, in addition to his 2-23, were match-winning and won him the player-of-the-match award for the fourth time in this competition.
But Jacks may not have been able to pull off the heist without 21-year-old Ahmed, whose six from the second ball he faced brought the chase to life in his first World Cup match.
His second, hit off the vastly experienced Santner, effectively sealed the deal.
Ahmed, who also took a wicket with his first ball, was picked for the conditions here. Can England really leave him out next week?
The big issue that remains is the form of Jos Buttler. He was out for a two-ball duck – his fifth single-figure score in a row.
Phil Salt also nicked off in the first over while Brook made 21, Jacob Bethell 21, Tom Banton 33 and Sam Curran 24 – all contributions but not match-defining scores.
Jacks and Ahmed ensured that will not be the focus, however. England may face India in Mumbai next week. What an occasion that would be.