Andrew Temple, 53, preyed on the victim from the age of eight and even molested her in a hospital.
Temple, of George Terrace, Loanhead, in Midlothian, had denied a string of charges during a trial at the High Court in Edinburgh.
But a jury convicted him of the seven offences he faced, including two charges of rape and three of indecent behaviour towards the girl and two further offences of indecency against boys aged eight and six.
Temple’s offending against the girl began in 1996 and took place at addresses in Easthouses and Dalkeith, in Midlothian, and in Fort William, including at the Highland town’s Belford Hospital where the victim was being treated and went on up to 2004. The boys were targets for his abuse in the 1990s.
The female victim, now aged 31, first spoke to police in 2003 but told the court that she was informed that there was not enough evidence to charge her abuser.
She later contacted police again in 2010 when she was feeling “really suicidal”. She said she had three overdoses and added: “I just thought ‘enough is enough’. Something needs to be done.”
She made a further contact with police in England in 2014 which eventually led to Temple being charged.
At one stage she handed a letter to officers in which she detailed some of the abuse that she suffered at the hands of Temple.
She wrote: “He started touching me, getting me to do things to him and having full sex with him.”
She said she remembered Temple offering her cider and she drank glass after glass until she was feeling “funny and sick”.
She recalled him pulling down her trousers and raping her. She said it hurt her and she wanted him to stop but he did not.
Afterwards Temple returned and asked her if she liked it and she told him “yes” because she felt really frightened. He told her not to tell anyone it.
Following his conviction the judge, Robert Weir QC, put Temple on the sex offenders’ register.
Temple, who was on bail throughout the proceedings, was remanded in custody while a background report is prepared on him ahead of sentencing next month.
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