The bottom line from a ­suitably intense, frayed and at times ­alarmingly open encounter is that the clouds around Manchester United are clearing. This was their fourth league win in a row and it offered the latest confirmation that, in Rasmus Højlund, they have a centre‑forward worthy of the handsome investment paid to Atalanta last summer. When Højlund converted twice in the first seven minutes, becoming the youngest player to score in six successive Premier League games, United appeared to have laid the platform for a straightforward evening. It is to Luton’s huge credit, and a reflection of the lessons Erik ten Hag’s side must still learn, that no such thing materialised. They responded through Carlton Morris and such was their application thereafter that nobody could have complained if Ross ­Barkley’s header had looped in, rather than clip the crossbar, for a sensational equa­liser in the final minute of added time. United could not have objected, either, if Casemiro had been sent off before the break during a period when Luton had the wind in their sails. Casemiro had already been booked when he went through the back of Barkley and it seemed ­lenient, to say the least, on David Coote’s part that he opted not to apply further punishment. It was little surprise to see Casemiro and Harry Maguire, who endured a torrid opening period and received a yellow card of his own for hacking Morris down, removed at half-time and United were largely more stable thereafter. In making such a barnstorming start United must have thought that, at a venue where all of the top flight’s giants have been given a dogfight, they might be the ones to emerge without a scratch. They pulled two goals clear through another exhibition of finishing prowess from Højlund, whose early struggles in English football are a fading memory. Luton’s defending made a hefty contribution, too. When Casemiro belted an early clearance upfield there seemed little threat to Amari’i Bell, who was facing the Luton goal as the ball bounced up. What should have been a simple pass back to Thomas Kaminski became a horrible, scuffed execution that the chasing Højlund anticipated adroitly. Confronted by Kaminski, the Dane manoeuvred leftwards and slotted into the vacant net. Only 37 seconds had passed and United sensed further reward, a deflected Marcus Rashford shot quickly testing Kaminski. Luton’s trademark aggression was conspicuous by its absence at that point and, when ­Morris’s clearing header from a corner found an unattended Alejandro Garnacho, they were exposed again. Garnacho’s 18‑yard volley was slicing wide of the right post until Højlund ­swivelled his upper body and diverted it across a wrongfooted Kaminski with his chest. The home team had been wide open, perhaps jolted by a warmup injury to their tone-setting striker Elijah ­Adebayo. They could have been killed off when Rashford surged through the ­middle only to shoot wide. But there had been signs, when Luton did progress the ball, that their left side might profit and they soon found a way back via exactly that route. It was Alfie Doughty, the ­indefatigable wing‑back, who centred intelligently for the ­former United youngster Tahith Chong to turn and shoot. Chong’s effort deflected up off Maguire into the six-yard box where a stooping Morris nodded past André Onana’s star jump. The tone had shifted dramatically. United rarely cope well with such changes in emphasis and, for the next half hour, were rocked by opponents who had finally discovered their bite. There was added grace in the midfield promptings of Barkley and Albert Sambi Lokonga; raw speed, too, in a bursting Chiedozie Ogbene when he brought a yellow card from Luke Shaw. Morris miscued another headed chance and then shot narrowly off target from 20 yards. Between those openings a sloppy Maguire pass had required Diogo Dalot to take ­evasive action before Cauley Woodrow, who had replaced Adebayo, could capitalise. Doughty, bursting through but ­clipping wide, missed a presentable chance to equalise. United went in feeling bruised and fortunate: Shaw departed with an injury before the whistle while boos rang out for Casemiro and the officials as a full complement of visiting ­players reached the tunnel. Scott McTominay and Jonny Evans were introduced to steady the ship but Luton continued to probe, a Doughty centre flying across goal. The excellent Chong then tricked to the byline but could not locate a teammate. United countered and Rashford forced a sharp stop from Kaminski. In truth, United should not have needed to hold their breath until the last. Bruno Fernandes could have offered relief on the hour but, after going past Kaminski at an angle on the right, he was denied by a heroic recovering block from Sambi Lokonga. Six minutes later, an almost identical situation involving ­Garnacho saw a combination of Bell and Kaminski keep the game alive. Luton sensed parity when the ball fell to Gabriel Osho six yards out but the defender could not get a clean strike away. Almost imme­diately, Kaminski, a formidable presence throughout, superbly denied Højlund a hat-trick. It would have been a vital moment if Barkley’s last-gasp attempt had been a few centimetres lower.