- 3 updates
Estimate, the racehorse which has tested positive for a banned substance, helped make sporting history for the Queen as she became the first reigning monarch to win Royal Ascot's Gold Cup.
The Queen was pictured beaming as Estimate crossed the line in first place during the dramatic race last year.
Prime Minister David Cameron congratulated the Queen in a tweet saying: ''Huge congratulations to Her Majesty for Estimate's victory at Royal Ascot - first time ever a reigning monarch's horse has won the Gold Cup.''
Her Majesty won £155,960 in prize money after Estimate's victory.
The Queen has been informed of her racehorse's failed drugs test, her majesty's racing advisor said.
Estimate, which won the Gold Cup at Royal Ascot in 2013, tested positive for morphine - a prohibited substance.
Sir Michael Stoute, the racehorse's trainer, is offering his "full co-operation" to the investigation, John Warren, from the Queen's bloodstock and racing advisor, said.
"Sir Michael is working closely with the feed company involved to discover how the product may have become contaminated prior to delivery to his stables,
"As the BHA investigates this matter, including potential links between the different cases, Sir Michael continues to offer his full co-operation.
"Her Majesty has been informed of the situation."
Estimate, a racehorse owned by the Queen and trained by Sir Michael Stoute, has tested positive for morphine, a prohibited substance, Buckingham Palace announced.
Initial indications are that the positive test resulted from the consumption of a contaminated feed product, the palace said.