Seddon put in an impressive chasing display to land the Magners Plate Handicap Chase at 20/1, carrying five-pound claimer Ben Harvey to a one-length victory over Richard Hobson's Fugitif.
The triumph was a first at the meeting for Meath-based McConnell , who has trained the horse to win three of his five starts since taking over the reins from previous trainer Harry Whittington.
"We were over the moon, he's done so much for us already and anything else was a bonus and what a bonus it is, to get a winner at the Cheltenham Festival," said McConnell.
"He's really well now. He came out of the race fine, we got him home and he's good, he's fresh."
Seddon used to run in the silks of the McNeill family before changing hands last summer, with former owner Max McNeill quick to offer genuine congratulations when the horse triumphed for new connections.
"I'm sure there were mixed emotions, but Max is a pure gentleman and he was very happy for the guys involved and for myself," said McConnell.
"I'm sure he was a little bit gutted that they weren't his colours, but that's understandable and no one expected that rejuvenation.
"Not anyone, not even ourselves, so who's to know?"
Seddon is likely to run again before the end of the season and there are a handful of paths McConnell could now take, with a return to hurdling not ruled out before his campaign comes to a close.
The trainer said: "There are so many options for him, from graded chases to big handicap chases and hurdles as well.
"He probably looks on a nice enough mark over hurdles I suppose, so that might be where we go next with him.
"We'll let him wind down for a week or two and see, but I'm sure he'll have a run before the end of the season."
In the aftermath of his Cheltenham heroics there was praise for Seddon not just as an athlete, but as a character too, and those were sentiments McConnell repeated when saying: "He's just an angel.
"He's an angel on the ground to deal with, with the kids he'll just stand there and get patted and eat his carrots. He just loves being a racehorse as well, you couldn't ask for a nicer horse.
"If you wanted a perfect racehorse, it's probably him."
