Samples were taken from the horse following an endurance competition in Doha on May 2 in 2015, with Darban having ridden to a fourth place finish.

The International Equestrian Federation (FEI) stated that the beta blocker propranolol, which is used to lower the heart rate, was discovered in the sample.

Propranolol is a banned substance under the FEI’s equine anti-doping and controlled medication rules.

The corticosteroid Dexamethasone was also found in the sample, with the anti-inflammatory medication currently a controlled substance under FEI rules.

The FEI stated in their final decision that the horse had been selected for testing due to a big and fresh jugular injection mark.

“In the opinion of the FEI, the person responsible has not provided any plausible explanation of how the propranolol and dexamethasone could have entered into the horse’s system,” the FEI stated.

Darban has been handed a two-year suspension, backdated to the date of notification of the positive test on June 23 in 2015.

His ban will now run until June 22 in 2017.

The Qatar based rider has also been fined CHF 2,000 (£1,570/$2,030/€1,840) and has been ordered to contribute CHF 1,500 (£1,200/$1530/€1,380) in costs towards the judicial proceedings.

Darban has been given 30 days, from the date of notification of the final decision of the case on July 7, to appeal the verdict to the Court of Arbitration for Sport.