Harry Cochrane, who won’t turn 17 until April, set Hearts on their way with a thrilling effort after 26 minutes. Kyle Lafferty squeezed the ball between the post and Craig Gordon’s despairing dive nine minutes later.
But this was only the half of it. Could Hearts keep this lead when the energy levels dipped and their young limbs cramped? They did more than simply maintain it, adding two further goals in the second half from the excellent David Milinkovic, the latter from the penalty spot.
It was all especially confounding given Hearts’ straitened circumstances. Hampered by injury and suspension, Levein had little option but to cherry pick from the Under-20s as well as ask more experienced players to perform out of position against the champions.
Hearts fielded a full-back, Michael Smith, at centre-half and he equipped himself well. But it was Levein’s confidence in two teenagers that proved the headline news. Jamie Brandon, a relatively ancient 19, was given the responsibility of handling James Forrest, perhaps Scotland’s in-form player of the moment.
At least Brandon had the good grace to be born before Hearts won the Scottish Cup in 1998. Cochrane entered the world three years afterwards.
He was asked to go up against Scott Brown, the Scotland skipper, and the physically robust Olivier Ntcham, himself only 21, in midfield. Not only did he outshine both, he also scored the goal that lit up the game. Anthony McDonald another 16-year-old, entered the fray midway through the second half as a replacement for Prince Buaben.
When Hearts scored their fourth goal they had three teenagers on the pitch. Levein was clearly enjoying the unlikely transition from perceived hoary reactionary to freewheeling promoter of youth. Young or old, there was not a failure in a maroon shirt. The aforementioned Milinkovic, no-one’s idea of a promising youth prospect and, in truth, suspected to be something of a journeyman, relished the occasion.
Even Scott Wilson, Hearts’ voluble PA announcer, was uncharacteristically rendered silent by what was unfolding in front of the new main stand.
A problem with the power supply meant half-time passed with just the murmur of crowd noise. It was a pleasant, refreshing change and emphasised that the real entertainment was taking place on the pitch, where Cochrane and Lafferty had already given Hearts some breathing space. This surprising state of affairs was contentedly digested by the home supporters along with their half-time pie. At 16 and eight months, Cochrane is the second youngest player to score for Hearts after Dave Bowman, in the early 1980s.
Both first-half goals were excellent strikes. A Dedryck Boyata ball out of defence was intercepted by Connor Randall and then transferred to Don Cowie, who laid a pass into the path of Cochrane. The teenager took a touch and then struck a sweet right-foot shot past Gordon from 16 yards.
Hearts’ second was again the result of slack play from Celtic. But then Callum McGregor was a long way from goal when he was robbed of possession. Milinkovic rolled a pass into Lafferty’s path and the striker took a few paces before hitting a lot shot into the corner of Gordon’s goal. Only the striker saw whatever little space there was at which to aim.
Hearts scored all their goals at favourable times. Few felt Celtic were out of the contest even when they were 2-0 down and so a third goal was required. Milinkovic supplied it just three minutes after half-time after a slip from centre-half Jozo Simunovic allowed the Hearts midfielder to advance on Gordon, who he then rounded before showing composure to slip the ball into the net.
A quick reply from Celtic might still have caused anxiety to rumble round three stands. But Hearts extinguished thoughts of a comeback when they scored a fourth after Gordon felled Ross Callachan, a replacement for Lafferty. With no obvious penalty taker on the pitch, and Levein gesturing for the players to sort it out themselves, Milinkovic took responsibility and confidently struck the award past Gordon.
The Hearts fans enthusiastically complied with Levein’s request for them to play their part. They cheered every throw won, every tackle contested.
There was an endearing moment in the second half when Cochrane, understandably caught up in the delirium of it all, challenged for a ball after it had been put back in by Hearts at a throw-in, with Leigh Griffiths expected to give possession back due to an injury to a home player.
Cochrane put up his hand to gesture an apology. None was needed. In the jaded world of Scottish football, it was intoxicating to see such verve, such promise.
Even the most ardent Celtic fan, their sense of romance dulled by the remorseless nature of their history-breaking unbeaten run, had to acknowledge this.
Fair play to the visiting supporters since the majority stayed to the end. They recognised the significance of the moment.
Not since St Johnstone defeated Celtic 2-1 in May 2016 have they seen their team beaten by a Scottish team. It’s been 77 games since they last saw their side fail to score in a domestic match.
Some Hearts fans joked beforehand that with a combined total of 74 unbeaten games between the sides, something had to give. It did. Just not in the way anyone expected.