Harrison defends his WBO title on 9 December against Nicky Cook

The WBO featherweight champion was incarcerated after being arrested in Malaga on 6 October for several alleged offences, including assault.

"Prison was ideal in terms of training preparations," the 29-year-old Scot told BBC Radio Five Live's Sportsweek.

"But not having the freedom to walk out of the gates and get out at any time was an absolute nightmare."

Harrison, who will defend his title against Nicky Cook on 9 December, has to return to Spain for another hearing on a date that is yet to be set.

"Once the gates are shut, there's no getting any kind of free time," he said.

I have had a good life up to now Scott Harrison

"After half-past seven at night I was banged up to half-past eight in the morning.

"Then you spend a few hours in the yard, then you have your lunch at two o'clock and you're banged up from two to five.

"You're trying to train and juggle your personal life as well - it's hard work."

Harrison insisted his career would continue "for years" despite his troubles with the law and problems with alcohol and depression.

Asked how he viewed his life, he replied: "That's a funny question.

"I'm 29 years old. That's something you should be asking me when I'm 70 or 80 years old.

"I have had a good life up to now. I've a long way to go, and a lot of goals I've set myself.

"I'm defending my title, and I can make history. I'll be up there with the likes of Willie Pep in the featherweight division.

"He is the longest reigning champion, and that's one of the major goals.

"I've smashed every record in Scotland, and I'm going to be in this game for years, so I'm more than happy."