Newcastle United owner Mike Ashley would be forgiven for having second thoughts about putting caretaker manager Chris Hughton in charge of first-team affairs on a permanent basis.
Hughton, due to be offered the job this week, now has his team playing like a Premier League team but unfortunately for the 2,000-plus visiting supporters who trekked down to Lincolnshire they are playing like the Newcastle side relegated to the Championship last season.
Thanks to calamitous defending and poor finishing, Newcastle suffered a humbling defeat thanks to Martyn Woolford goals either side of Kevin Nolan's strike.
Newcastle went into this game without having scored for 200 minutes since Marlon Harewood struck and Hughton responded by dropping the striker and Peter Lovenkrands with Geremi and Jonas Gutierrez handed starting slots.
Hughton's changes nearly paid early dividends but Joe Murphy saved superbly to keep out a header from Kevin Nolan, deployed behind striker Andy Carroll, following Jose Enrique's enticing cross.
It was a case of deja vu as Nolan was foiled by Murphy when he attempted to flick in Enrique's near-post cross only to see his effort diverted to safety off the Irish international's chest.
Typically, though, Newcastle's defence looked vulnerable and Gary Hooper shot wildly over from close range after Hughton's defenders failed to cut out left-back Marcus Williams' excellent cross.
Newcastle lost their early fluency provided by Gutierrez and Enrique, as passes repeatedly went astray and Scunthorpe should have taken the lead but Paul Hayes failed to hit the target from a favourable position.
Then midfielder Sam Togwell raced clear of Geremi when Zurab Khizanishvili failed to cope with Murphy's punt forward but Steve Harper saved a weak shot comfortably.
Back came Newcastle and Nolan cursed himself after hoisting the ball over the crossbar after a fine cross from the industrious Jonas Gutierrez who combined well with Enrique throughout the opening period.
But Newcastle continued living dangerously and when Rob Jones nodded down Josh Wright's free-kick, Woolford scuffed a proverbial sitter wide. Newcastle striker Andy Carroll proved more accurate but Murphy pushed his low drive wide.
Hughton's side re-gained the upper hand after the break and David Mirfin intervened to block Carroll's goal-bound effort before Enrique burst forward only to see his low 25-yarder zip narrowly wide.
However, the warning signs were there for Hughton to see as Hayes outjumped his markers to give Hooper the chance to take aim and his shot rattled the outside of Harper's post.
Scunthorpe went ahead in the 54th minute as Khizanishvili was out-muscled by Hooper as he back-tracked and the striker was allowed the square the ball to Woolford, only in the side due to Michael O'Connor's suspension, and he calmly beat Harper in front of a record attendance at Glanford Park of 8,921.
Exactly 13 years to the day since Newcastle beat Manchester United 5-0, Hughton's team raised their game and Nolan equalised with his seventh goal of the season when he finally got the better of Murphy, after being teed up by the enterprising Guthrie.
A point would have propelled Newcastle back to the Championship summit but then Togwell nodded forward and the unmarked Woolford beat Harper comfortably in the 79th minute to secure a famous victory for Scunthorpe.
Scunthorpe United (4-4-2): Murphy; Byrne, Jones, Mirfin, Williams; Woolford (Thompson) Togwell, McCann (A Wright 90), J Wright; Hayes, Hooper (Forte 79).
Subs: Slocombe (g), Sparrow, Spence, Canavan.
Newcastle United (4-4-1-1): Harper; R Taylor, Simpson, Khizanishvili, Enrique; Guthrie (Ranger 87), Geremi (Harewood 62), Smith, Gutierrez; Nolan, Carroll.
Subs: Krul (g), Lovenkrands, Kadar, Tozer, Donaldson.
Referee: A Penn (West Midlands)