An afternoon of electrifying tension, with an astonishing finale, ended in bemusement then unbridled celebration as Hull came back from a goal down for a point that takes them up to the Premier League as runners-up to Cardiff.

The crowd's joy was confined until the news came through, some 15 minutes after the final whistle here, that Hull's rivals for the second automatic promotion place, Watford, had lost 2-1 at home to Leeds.

Cue the crowd on the pitch, legitimately this time, on and communal cavorting to "Celebration" by Kool and the Gang.

All's well that ends well, but neither manager had seen anything quite like this – a red card, a pitch invasion and two penalties, all in added time. The Cardiff manager, Malky Mackay, said: "After that, I'm off to lie in a darkened room somewhere," and Hull's Steve Bruce exclaimed: "I thought I'd seen it all when Brentford played Doncaster last week, but this tops the lot."

One of Hull's goalscoring heroes, Paul McShane, added: "It was surreal really."

Cardiff had taken the lead in the 49th minute with Fraizer Campbell's seventh goal in 12 Championship appearances, but Hull's Tigerish pursuit of promotion had its reward with two in five minutes, from Nick Proschwitz and McShane.

With the issue seemingly decided the Cardiff captain, Andrew Taylor, was sent off for his second yellow card. Then, when Hull were awarded a penalty, for Ben Turner's foul on Ahmed Elmohamady, their fans invaded the pitch and play was held up for it to be cleared before Proschwitz could take the kick, which David Marshall saved.

Remarkably, Cardiff were then awarded a penalty of their own, for handball, safely dispatched by the substitute Nicky Maynard, and Marshall produced another top-class save to keep out Elmohamady's 20-yard free-kick.

For what was billed as the biggest match in Hull's history Bruce made the brave decision to switch from the 3-5-2 formation he had used all season to an orthodox 4-4-2. It was time for a change after three games without a goal against opposition that was modest at best. His team had previously lost to Barnsley and Wolves and managed a goalless draw against relegated Bristol City.

Cardiff, for the second Saturday in succession, lacked incentive against opponents with everything to play for. They gained promotion nearly three weeks ago and won the divisional title the following weekend. That their season was effectively over was underlined by the fact that they had already pensioned off their leading scorer, Heidar Helguson, on a free transfer, three months short of his 36th birthday.

In his place they gave a first start in the Championship to Etien Velikonja, the Slovenian international striker for whom they paid NK Maribor £2m last summer. He was preferred to Rudy Gestede, Campbell and Maynard, none of whom were fully fit. Velikonja lasted until half-time when he gave way to Campbell who, as if to suggest he should have been on from the start, scored within four minutes of his introduction.

As might have been expected, Hull pressed forward urgently from the start and George Boyd had the ball in the net after eight minutes, albeit from an obviously offside position. Turner then made a vital tackle to dispossess Robbie Brady as he set his sights on Marshall's goal.

With Hull making all the running it was the 20th minute before the champions had a decent strike, Craig Conway seeing his shot, from the left, deflected inches wide of the far post. Jordon Mutch was just as close in identical fashion.

Brady, persistent to the point of selfishness, wasted a clear-cut chance, scooping his shot over the bar when well placed, then blasted a free-kick from 25 yards into the defensive wall. When he finally located the target, with a meaty drive, Marshall denied him with a flying save.

Just before the interval the biggest cheer of the first half greeted the news that Watford were losing. Their equaliser quickly cut the celebrations short and depression was the order of the day after 49 minutes, when an inch-perfect through pass from Kim Bo-kyung enabled Campbell to go clear and beat David Stockdale with cool expertise. "One-nil to the champions" chortled the 2,100 Cardiff fans.

Hull drew level after 58 minutes when Marshall beat out a shot from David Meyler and in the consequent confusion Stephen Quinn found Proschwitz, who bundled the ball in from three yards.

Four minutes later there was pandemonium when, from Brady's corner on the right, McShane completed the transformation from deficit to profit side-footing home at the far post. But the late equaliser from Maynard, making his comeback after knee surgery, condemned the Humberside legions to a nail-biting wait.