Britain's Queen Elizabeth's horse has failed a drug test. Moonlit Path, one of 41 racehorses owned by the 83-year-old monarch, tested positive for Cyklolapron, which contains the banned substance tranexamic.

The six-year-old was checked after finishing sixth in a novices hurdle race at Huntingdon, Cambridgeshire, in February and the queen is said to be very disappointed by the news.

A source said: "It is fair to say horseracing is Her Majesty's one great passion in life. The fact that one of her own mares has failed a drugs test will come as a bitter blow."

Cyklolapron is used to stop horses from hemorrhaging as they regularly suffer from nose bleeds before and during races.

Moonlit Path's trainer Nicky Henderson, an old friend of the queen's, has been charged by the British Horseracing Authority.

They claim Henderson gave the horse the substance "with the intention of affecting her racing performance or in the knowledge her racing performance could be affected."

Henderson - who is due before a disciplinary panel next month - told Britain's The Sun newspaper: "The substance was administered by my vet entirely in the interests of the horse's welfare, which is paramount."

"There was no intention to enhance performance and it is worth pointing out we won the race in question with the odds-on Ravello Bay."

The queen's racing manager Sir Michael Oswald said: "This is a matter for the British Horseracing Authority. The queen has been informed."