Arctic Fire was second in the Champion Hurdle two years and has proven course form having also finished fourth in the County Hurdle (2014), but he's 418 days off the track and it'll be very hard to compete off top-weight in the Grade Three handicap hurdle (2.10).
The Jonjo O'Neill-trained Minella Rocco came from off the pace to deliver a withering late run, snatching second on the line from the tiring Native River, while Djakadam was less than a length back in fourth.
Power said: " The first day I rode him, I said he would go further.
"I only got them in September, I had to get to know them, how to train them". This is the jewel in the crown.
The seven-year-old had failed to complete on his last two runs but found plenty in the closing stages to pass Native River and claim second in chasing's blue riband.
"There was never any thought that Sizing John was to join the Potts' horses who went to Colin Tizzard - this horse was already in my yard".
"I always said when this horse stepped up in trip he'd win".
"When he won at Thurles he didn't win until stamina kicked in and that convinced me he'd stay".
Power added, "The one thing about Sizing John is you can rely on his jumping".
It looks very much like it could be third time lucky for the eight-year-old who looks to be the ideal age and candidate to win a Gold Cup which is obviously missing a few high-profile stars.
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Dad deserves a lot of credit for changing his routine completely at home in an effort to get him sparkling again, while Ruby timed his run to perfection on a day when his unrivalled class in the saddle was clear for all to see after earlier giving a masterclass on Un De Sceaux, the most exciting horse in training, and Yorkhill.
I ride Aupcharlie, which was only beaten four lengths by On The Fringe previous year, for Jim Dreaper in the amateur riders version of the Gold Cup (4.10) and I'm excited to have a good ride in this race. "He had it over two miles behind Douvan and he has that bit of speed".
Remarkably, Power and Harrington teamed up with Rock the World for another victory in the Grand Annual Chase, the concluding race of a dream Cheltenham for Ireland.
"It's our first runner in the race, the jockey's first ride and Jessie's first runner".
Won Festival race - Ryanair and come second in the Arkle.
Former Grand National winning jockey Robbie Power rode Sizing John and was quick to praise the Irish horse's trainer. In so doing, he claimed his sixth victor of the week to tie with Mullins but he won the title on countback to placed runners.
"The mistake cost me second place but I don't believe I would have done better than that", said the 37-year-old Irishman.
"It is out of relief as he has been favourite all year", said Hobbs.
Death Duty should go off favourite in the Albert Bartlett.