Leeds United and Derby County will always have a rivalry because of 'Spygate'.
In one of the most incredible stories of the 2018/19 season, Derby alerted the police after a man with binoculars was found spying on them during one of their training sessions.
It turned out that the man was a Leeds employee.
Of course, Frank Lampard and Derby weren't happy, and they would have been even angrier when they were beaten 2-0 at Elland Road a couple of days later.
The two teams were then drawn to play each other in the Championship play-off semi-finals, with a lot of the build-up to the game dominated by 'Spygate'.
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It looked as if Leeds would emerge triumphant after they won the first leg 1-0 at Pride Park.
They then took an early lead at Elland Road to make them almost certain to progress to the final.
But Derby produced a wonderful comeback.
Lampard's side turned the tie on their head as goals from Jack Marriott, Mason Mount and Harry Wilson gave Derby the lead with 30 minutes remaining.
Stuart Dallas found the corner of the net to restore parity but, after Leeds went down to 10 men, Marriott struck with five minutes remaining to send them to Wembley.
And in their post-match celebrations, Derby players felt the need to rub salt into Leeds' wounds.
While celebrating with their fans, a number of Derby players used gestures to mock the incident.
Watch it below:
Jayden Bogle, Fikayo Tomori, Mason Mount and Scott Malone - take a bow.
Lampard also admitted that the victory was made sweeter by the 'Spygate' controversy from earlier this season.
"Maybe, maybe [it is sweeter]. I'm not gonna lie maybe it is," he told Sky Sports, per the Mirror.
"I heard a lot of people saying that we were crying about Spygate but I haven't thought about Spygate for a long time.
"We played them, we prepared, and we got a result.
"Everyone had written us off. Everyone thinks they're beating us three times.
"There's work to do, we're underdogs again.
"We'll have a tough game a Wembley against a brilliant Villa team, but we're there."News Now - Sport News