A York man is today starting a life sentence for corrupting and repeatedly raping two brothers aged six and 13.
Judge Paul Hoffman branded Bryan Stanford dangerous, scheming and manipulative after hearing the catalogue of his crimes against children.
A known paedophile on the sex offenders register, the 51-year-old deliberately evaded police checks to prey on his victims, York Crown Court heard.
He has already served 10 years for kidnapping a girl in Norfolk in front of her friends, raping her in a vehicle and then threatening to kill her unless she kept silent.
Judge Hoffman said "particular great care" must be taken before Stanford is allowed parole and "let loose on the community".
He praised DC Dave Peat, who was crucial in bringing the paedophile to justice, as a "very impressive officer" whose work was a "shining example".
A jury convicted Stanford of three rapes and five indecent assaults on the boys and possessing pornographic photographs of the six-year-old with intent to sell them.
Stanford, of Thorn Nook, off Malton Road, York, previously admitted two charges of taking the photographs.
Jailing him for life, Judge Hoffman said: "You are a scheming and manipulative and highly plausible paedophile with quite an appalling record.
"You insinuated yourself into the (boys') family, you ingratiated yourself with them by means of lavishing gifts, you cultivated them and their children, you were the proverbial viper in the nest because when the (parents') backs were turned, you were corrupting their children in an unspeakable and unnatural way.
"You are, in my view, a dangerous man where young children of either sex are involved."
The jury took just over four hours to deliver their last verdict. Five were unanimous, four by a majority of 10 to two.
Stanford brought the older boy to York and raped and abused him in his flat over two days, then repeatedly raped and abused the younger boy in the brothers' home, the court heard.
He was 16 when he committed his first sex offence, an attempted rape, and in 1997 he was jailed for 15 months for three indecent assaults on children committed as a young man. He also has numerous convictions for violence and dishonesty.
After his release, he gave the police his York address, but did not reveal his constant visits to the brothers who live outside Yorkshire.
Following the sentence, DC Peat of the Family and Protection Unit for York and Selby said: "He is one of the most evil and dangerous men I have ever met. Society and children in general have been protected by the verdict from an evil man."
Stanford's barrister James Chadwin said he continues to deny the kidnap and rape for which he got a 10-year sentence.
As a child, he had been inadequately fed, abused physically by his mother and raped by her lover.
Stanford's solicitor Kevin Blount said outside court: "We will be advising our client on an appeal. He has maintained his innocence throughout."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article