Having suffered a short-priced defeat with Getabird in the curtain-raising Supreme Novices' Hurdle, Footpad was the 5-6 favourite to get Mullins and his stable jockey Ruby Walsh off the mark at the 2018 Festival and it proved to be a fascinating affair.
Walsh, who only last week returned to action having been sidelined since suffering a broken leg in November, was coolness personified as he settled Footpad well off the furious gallop being set by his old foe Petit Mouchoir and the chief British-trained contender Saint Calvados.
Footpad gave his supporters a real scare when banking one of the fences in the back straight, but he soon recovered and with Saint Calvados weakening quickly not long after, Walsh set his sights on Petit Mouchoir and Davy Russell.
There was not a lot between the big two jumping the second fence from the finish, but it was clear Footpad had far more to give and much to the delight of the majority of punters at Prestbury Park, the French-bred gelding powered clear in the straight to score by 14 lengths.
Mullins said: "The two front runners went a real good gallop and Ruby was happy to leave them at it. The thing that probably wasn't in the script was for him to make that mistake at the first one down the back.
"I wondered could he recover from that on that ground. Ruby just sat and he played the hand he wanted to play.
"I'm not sure whether my heart can take it anymore! He was so far back midway through the race, but Ruby showed nerves of steel."
He went on: "We know he stays. It's a surprise to us that he's able to win an Arkle. We had him down as our two-and-a-half-mile horse for this year, JLT or possibly RSA, but then when he came out and did what he did in his first two races we said we were in the wrong division and should go back for the Arkle and he's done that now.
"I doubt I've had one improve so much from hurdles to fences. His jumping has just brought him up another gear.
"This fellow could be a Gold Cup horse. Lots of Gold Cup horses have won the Arkle and this fellow is much more laid back than some.
"I think we will have a good chat with connections and see if they would like to go in that direction.
"He has plenty of stamina."
A jubilant Walsh had the luxury of being able to salute the crowd as he passed the post.
He said: "It sent the hairs down the back of my neck
"He was brilliant. I can't say I was confident when we landed at the back of the first down the back, but I was kicking myself I went too fast in the first and thought they can't keep going and would come back.
"It's been a long old winter and this makes it worth it."
Henderson said: "His jumping was great. Both Nico (de Boinville) and Ruby knew that was some pace up front and they weren't going to go with them.
"Those boys were right and they've sat and we've just grabbed second in the end.
"He's ran a great race. He is good, though."
Petit Mouchoir's trainer Henry de Bromhead said: "Davy felt he possibly went too quick but he was jumping and travelling so well he just let him roll.
"Unfortunately he then fell in a bit of a hole but it was only his third run over fences after an interrupted season.
"All being well he'll be at Punchestown."