Colin Tizzard is fully aware of the size of the task that he has set his star horse when he runs in the William Hill King George VI Chase at Kempton Park on Boxing Day.

Cue Card has already proven himself a top two-miler but now he will be mixing it with the elite three-milers and hoping to follow in the hoof prints of Desert Orchid who won the King George at his first attempt at three miles in 1986. But many others have tried the same and simply failed to stay the extra distance.

Three years ago it was the size of the opposition that scared Tizzard when he took Cue Card to the Cheltenham Festival for just the second run of his life. "When I saw him in the Champion Bumper pre-parade ring with the ones that Willie Mullins was running, they were half as heavy again," Tizzard recalled with a grin. "But he's not that any more. He's now grown into a big, strong horse who's pushing 16:3 and, from day one, he's always done it all so much easier than any other horse we've had."

Cue Card did it easily that day at Cheltenham as he beat Al Ferof by eight lengths. The two were due to meet again in the King George until Al Ferof was scratched for the rest of the season with a leg injury.

His trainer, Paul Nicholls, can find a replacement from his well-stocked yard, but Tizzard knows this is his best shot in the locker. Tizzard also knows that he can only do so much to have him ready for the race. "He's the best we've had – and I'll be surprised if I get one better than him," he said. "But the nature of the beast is that they can do damage on the gallops or in their box. It's just trying to make sure we can do everything we can to stop it happening."

Tizzard's strategy has been to run Cue Card against the best around and his short-head defeat to Bobs Worth, now the ante-post favourite for the Cheltenham Gold Cup, last season when trying to concede 7lbs shows he has every right to do so. Cue Card came back this season to win the Haldon Gold Cup at Exeter by 26 lengths after which the trainer and his jockey son, Joe, decided to have a crack at the King George.

"If you go back through his Champion Bumper, his hurdling and novice chasing campaign, we've never shied away from anyone," Tizzard said. "We took on Sprinter Sacre in the Arkle last season and we ran into one of the best novices we've seen – but it didn't do our horse any harm and he finished second.

"His first-time-out efforts have been brilliant which is why we purposely left him from the Haldon Gold Cup to the King George to try to keep him fresh. He's pleased us immensely in a schooling session on Monday; Joe came back and said he's never felt so good. All his form stacks up, but we're in a really hot race aren't we? They'll be no place to hide, that's for sure."

The simple truth is that a two-miler cannot win the King George. Desert Orchid, who blitzed his field into submission 26 Decembers ago, did so because he could stay every yard of three miles and more. The same was true of Edredon Bleu, who won the 2003 King George three years after he had won the Queen Mother Champ-ion Chase.

But the King George is littered with the names of speed horses who have found those final furlongs too much. The prospect of testing ground means this will be anything but a soft option for Cue Card but Tizzard remains undeterred. "People say he won't stay. Why's that? Because he runs so fast? That doesn't mean he won't stay. He can go a top-class pace on the bridle. We'll find an awful lot more out about him at Kempton. If we get beat, we get beat. It won't be the end of the world."

And that, for Tizzard, is about the size of it.