IMPEK, one of the leading lights of Henrietta Knight's West Lockinge stables, near Wantage, has been ruled out of the Stan James King George VI Chase at Kempton on Boxing Day after going lame.

The ten-year-old (pictured), a creditable third to Kicking King in the Christmas showpiece 12 months ago when it was run at Sandown, was as low as 10-1 in places for this year's race.

Impek had started this season in great style with a runaway victory in the William Hill Gold Cup at Exeter.

However, he then suffered from a muscular problem in his shoulder that forced him to miss the Peterborough Chase at Huntingdon.

And now his preparations have been hit by a further setback.

"Impek won't make the King George as he's gone lame again," said Knight.

"He had been back in full work, but he does go intermittently lame and after his problems, he's going to need a length of time off for it all to come right. I shouldn't think he will run now until the spring."

In Impek's absence, Knight's hopes of a third King George - following the wins of Best Mate and Edredon Bleu - will rest with Racing Demon.

Priced at 6-1 third favourite with the sponsors, the highly-rated gelding was last seen decisively winning the Peterborough Chase.

"He was always going to be a runner there, and is in good form," reported Knight.

Following the news of Impek's defection, Coral now make the Paul Nicholls-trained Kauto Star their 4-6 favourite for the King George.