'I didn't use any drugs and was very surprised when the stewards told me I had a positive test result,' Leung said.

'I've never touched ketamine in my life, but now I have been suspended for six months I realise that people are not going to believe me.

'I don't know if I had my drink spiked, but I do know I should not have tested positive to any drugs.'

Leung, twin brother of fellow apprentice Derek Leung Ka-chun, did nothing to fight the charge.

He took the punishment and was sent to Canada by his father to escape the controversy. He has watched on as more than 375 races were run during his absence. But now he is hungry to ride winners and determined to clear his name.

'Everyone will think that maybe I am now feeling sorry for what I did, but in my heart I know I did nothing wrong,' Leung said.

'I have no idea when I might have ingested the drug either. I thought about it a lot when I was stood down in September but I can't pinpoint it.

'I went to a barbecue with some friends a few days before I tested positive and we were all having a few drinks, but no-one was using any drugs. I hadn't been to a nightclub or anything like that either, so it was a real shock.

'At first I was very sad to be in this situation, but now I just want to show all the people that doubted me that I am going to put it behind me, concentrate on working harder and get back to riding winners.''

Leung's Canadian sabbatical improved his command of English and also motivated him to avoid the fate of fellow jockey Marco Chui Kwan-lai, who was recently refused a riding licence after returning from his second ketamine suspension.

Like Leung, Chui was suspended for six months for his first offence, but tested positive again within two months of returning to the saddle.

He earned a year-long suspension for his second breach of the prohibited substances rule, which spelled the end of his career in Hong Kong.

Leung said: 'My family sent me to Canada to live with my auntie for three months, to get me away from Hong Kong and any bad influences or bad friends.

'I spent that time taking English lessons and keeping fit. It was the first time I'd been to Canada and it was a good break for me.

'I came back in December and have been living with my father in Wong Tai Sin. I'm not allowed to work at the stables or ride trackwork yet so I've just been doing fitness work.

'My master Me [Tsui Yu-sak] is writing a letter to the stewards to ask if I can come back to the stables soon, so hopefully I will be back riding trackwork in a couple of weeks.'

Until then, Leung has been pushing himself physically to get as fit as possible ahead of his March 8 return, and will be using every day he gets at trackwork to get back his 'race fitness'.

He said: 'My weight is still okay. I have never had any worries with that because I am naturally light.

'But I have been running 10 kilometres every day up to Ma On Shan and have been playing tennis, riding my bike and going to the gym to mix up my routine,' he said.