While tonight's mouthwatering Super League elimination play-off between the fierce foes is being dubbed as the most important since Rovers' famous 1980 Wembley Challenge Cup final win, they did also meet in the John Player Trophy final five years later at Boothferry Park.
A then-record 25,000 fans crammed into Hull City's icy, snow-covered ground to see scrum-half Harkin out-play Australia legend Peter Sterling and inspire a 12-0 success.
There has not been a bigger derby attendance in the city since and man of the match Harkin recalled: "With that final being actually in Hull, getting one over our rivals in our own backyard made it all the more enjoyable.
"The supporters were fantastic back then, it was a great day and I'm sure it's going to be another amazing derby come Saturday night."
A frustrated travelling reserve in 1980 and Challenge Cup loser against Widnes the following year, Harkin's duel with Sterling was crucial to Rovers' inaugural victory in the competition though he admitted initially being over-awed.
"He had been man of the match when they beat us in the Yorkshire Cup final a couple of months earlier," said the ex-Wakefield, Bradford and Halifax No 7.
"Sterling had come over to England and everyone was blazing about him but, before the JP final, I remember Len Casey coming over to me and saying how this lad's supposed to be the world's best and 'are you going to have a go at him?' He basically said if I don't give him (Sterling) a crack, he'd give him one himself.
"Nobody had tested him or seen what he was about but, for all he was on top in the Yorkshire Cup, that day was mine. I got a good kicking game going and we just got a roll on from there."
Harkin added: "Everything went great.
"I give him his due though, Sterling came over to me after the game and told me I should be playing in Sydney. He said I needed to go, to move on and, not long after, I went out to play for Brisbane Valleys who Wally Lewis had been playing for.
"I thought I'd be playing alongside him but he moved on to Wynnum Manly."
The fascinating battle between current scrum-halves Sean Long and Michael Dobson will be vital this evening as the city rivals bid to progress towards the Grand Final.
"I think it is going to be very, very close and it is too close to call," said Harkin. "We always said form went out of the window on derby day.
"I'd maybe go for Rovers but seeing how Hull performed so well with just 12 men against Leeds last week, who knows what might happen?"