Top chaser, Malborough, has been sidelined with a traped epiglotis and will miss the King George V1 Chase on Boxing Day

Marlborough, a leading contender for the Cheltenham Gold Cup,could be out of action until the New Year.

The Nicky Henderson-trained chaser had been an intended runner in Saturday’s Hennessy Gold Cup at Newbury, but has been found to be suffering from a trapped epiglotis, which will require an operation.

The problem only came to light on Monday during a routine trachea wash. “Everything had been going to plan,” said a shocked Henderson. “It is a rare complaint but needs correcting and Marlborough will undergo routine surgery this week.”

Marlborough will also miss the mid-season showpiece, the King George V1 Chase at Kempton on Boxing Day.