On 77 minutes up stepped Kobbie Mainoo with the coolest of ­winners in front of the Stretford End to cause bedlam among home fans and wrest the bragging rights Manchester ­United’s way.

Alexis Mac Allister’s weak clearance rolled to the midfielder who beat Dominik Szoboszlai to punch home a finish that beat Freddie Woodman to the Liverpool goalkeeper’s right.

After ceding a 2-0 half-time lead this ensured a league double over the visitors for a first time in a ­decade. Yet as United and Liverpool are not in the title race this meeting of ­England’s heavyweights was akin to two ­follicly challenged men fighting over a comb.

Michael Carrick and his team were far happier – as victory confirmed what was all but a (mathematical) ­certainty: United are back in the Champions League and the interim manager can afford to be baffled if he is not offered the post on a ­permanent basis.

His record is 10 wins, two draws and two defeats from 14 games: 32 from 42 possible points is a stellar return, particularly as the 3-4-3 of Ruben Amorim plus his predecessor’s mercurial persona had sapped morale and confidence when he arrived in January.

After the interval United folded, allowing Arne Slot’s side to respond to Matheus Cunha and Benjamin Sesko strikes with goals from Szoboszlai and Cody Gakpo. Each derived from errant United passes, from Amad Diallo for Szoboszlai’s and Senne Lammens for Gakpo’s equaliser.

United were as lively at the start as they had been against Brentford on Monday, launching several raids down the right flank. Following one, Bryan Mbeumo’s corner from the right bounced to Cunha. A first effort came back via Ryan ­Gravenberch. This time, with his left boot, Cunha’s shot caromed off Mac ­Allister and beat Woodman to his left and home celebrations began.

Soon, there were more chances as United’s thrust shredded ­Liverpool. Again, from the right, Bruno ­Fernandes crossed for Sesko who was impeded and did not finish. Down to the turf went the striker, who sprang back up as the attack continued. This time Luke Shaw, from the left, popped the ball over for the ever-threatening Fernandes. He flicked a header back, this was palmed by Woodman on to Sesko who, falling over once more, bundled in United’s second. Slot moaned there was a handball by the scorer but images were inconclusive.

Two-nil down 14 minutes in was the visitors’ worst nightmare and Liverpool were unable to breach United territory. Slot’s 4-2-2-2 formation – due to Alexander Isak’s absence – that positioned Florian Wirtz and Szoboszlai as the (false-ish) 9s was near-toothless.

Liverpool’s issue was allowing United too much space. ­Fernandes missed a simple opening – for him – from a Mbeumo cross, cannoning the attempt wide, as he and the winger were unmarked.

Slot’s side were ragged. Szoboszlai, supposedly their totem, and Wirtz misplaced passes, and the pace was too fast for all in white.

Slot was reduced to arm-flailing frustration after Jeremie Frimpong, in for the injured Mohamed Salah, was caught offside, the crime more blatant as this was during a soporific buildup rather than quick counter.

As the news filtered through of Sir Alex Ferguson being taken to hospital as a precautionary measure due to feeling unwell, the former manager, who is said to be out of harm’s way, would have been proud of United’s front-foot mode.

One of Cunha and Sesko should have netted a third as the interval neared. Then, in the period’s added time, Fernandes floated a corner over from the left: it amounted to nothing, unlike the 45 minutes, generally, for United.

For the second half Diallo replaced Sesko due to a shin problem, the ­Ivorian hugged by Carrick as he headed on. The decision backfired immediately when the winger spilt the ball to Szoboszlai near the ­centre circle.

He skated forward, Harry Maguire backed off and kept doing so, the Hungarian slalomed right of ­Lammens’ goal, then coolly rolled beyond the keeper into the left ­corner, Diogo Dalot perhaps unsighting the Belgian.

This was superb from Szoboszlai, calamitous from Diallo and ­Maguire. So what finer riposte than a fluid home move? It featured Casemiro spiralling the ball in, Fernandes pinging it across from the right, and Mbeumo’s backheel defeating ­Woodman only for the right post to save Liverpool.

Nothing saved Lammens when the usually reliable goalkeeper ­produced a clanger. Aiming for Casemiro he found Mac Allister lurking. The Argentinian tapped to Szoboszlai and as the hapless Lammens rushed out Gakpo was found and he made the score 2-2.

Lammens grimaced, Carrick was dumbfounded, and the visiting supporters partied. Liverpool were ­inferior in all but spirit: enough to draw level and stymie United, who now had more of the contest coming at them. Example: Szoboszlai swung in a free-kick, United’s rearguard ­slumbered and Lammens stabbed the ball off the line.

Now, though, came Mainoo’s clincher and United remain headed for a third-place finish.