A British man was convicted of raping two teens for over a decade and in one instance, allegedly forcing one of them to witness him sexually abusing a dog.

Karl McLeish, 54, was convicted of 13 counts including rape, attempted rape, sexual assault, indecent assault, and sexual touching on Wednesday by a Liver Pool Crown Court jury. He was sentenced to 18 years in prison. He was also ordered to sign the sex Offender's Register for life.

Investigators found that McLeish traveled to various locations in the United Kingdom with his two victims, including St. Helens, London and Somerset, where he would shower them with gifts and treats and often ply them with alcohol before sexually abusing them, Liverpool Echo reported.

His first victim was an unidentified 16-year-old boy whom he met while on a trip to London. After offering the victim alcohol, he proceeded to touch the teen’s penis. The court heard how McLeish’s abusive behavior had "devastated" the life of the first victim. The latter had lost a lot of weight and had turned to drugs to deal with trauma.

In one of the instances of rape, the victim was "scared and crying, but you just carried on," Presiding Judge Murray said. Prosecutor Martine Snowdon said, “ He has been unable to move on from it.”

The second victim, also a boy was 14 years of age when the convict was paid to look after the teen. While the abuse in that case started with McLeish touching him over his clothing, it soon escalated to rape. The convict began throwing the victim on the bed and sexually assaulting him.

"You were in a position of trust and you groomed him. You took him to events around the country, you got him gifts and said you'd give him cigarettes...you showed him pornography...you told him you would batter him if you didn't return."

The years of abuse caused the second victim to lose his trust on people and was is in a "constant state of vigilance at college." Even as an adult, he continued to face night terrors, and often woke up screaming. He had to keep the light on at night and also wet his bed at times – a condition he found “embarrassing.”

"He is in constant fear of McLeish coming back,” Snowdon added. “He cannot understand why these terrible events happened....he's threatened to take his own life and so his family has to know where he is and that he is safe."

Perhaps the most shocking crimes that McLeish was accused of was engaging sexual activity with a dog and forcing one of his victim’s to watch. One of his victims was afraid of coming forward with the accusations of the abuse because he was afraid of the repercussions.

McLeish remained impassive and unmoved in the court when the case was being made against him. Murray said he believed that sexual offending was “entrenched” in the convict since he had been committing it for a span of 14 years.

A British man was convicted of raping two teens for over a decade. In this photo, a prison guard at HMP (Her Majesty's Prison) Pentonville stands behind a locked gate in London, May 19, 2003. Getty Images/ Ian Waldie