Two vulnerable women with learning disabilities were involved in Muslim marriages to Pakistani students fighting to stay in the UK, High Court judges have heard.
One man had begun a relationship with a woman in her late teens two months after exhausting his rights of appeal.
The second married a woman in her 30s about six weeks after his application to stay was refused by immigration authorities. An anonymous informant had called to tell officials that the woman's stepfather had received £20,000 "in consideration" of that marriage.
Details have emerged in two written rulings published on a legal website following separate hearings in the Court of Protection in London. Judges said no-one involved in either case could be named.
The Court of Protection is part of the High Court and judges make decisions about sick and vulnerable people.
In the first case, a local authority had asked Mr Justice Keehan to make rulings about whether the teenager had the mental capacity to make decisions about her life - including the capacity to decide about entering into a "contract of marriage".
He said social workers became aware that she had begun a relationship with a Pakistani man in his 20s.
Local authority officials and police had warned that the man might commit an offence because the woman was unlikely to have the capacity to consent to sex and marriage. Nevertheless the couple had "entered into a purported Islamic marriage ceremony" at the man's home about 18 months ago.
Mr Justice Keehan said the man had arrived in the UK to study in 2009 but an application to stay was refused after an immigration tribunal concluded that he had submitted forged documents and attempted to deceive officials.
"His rights of appeal were exhausted in June 2011," said the judge. "It is in this context that he began a relationship with (the woman) in August 2011."
The judge said that days after the marriage ceremony the man had claimed asylum because "he feared he would be killed by his family who disapproved of his marriage to a white British woman".
He said the man had been refused asylum and deported in August 2012.
Mr Justice Keehan concluded that the woman had the capacity to consent to sexual relations but said she did not have the capacity to enter into a marriage contact. And he ruled that the wedding ceremony she had been involved in was a "non-marriage".
In the second case, a local authority had asked Mrs Justice Parker to make decisions about whether the woman in her 30s had the capacity to consent to marriage and sexual relationships.
The judge said the woman had taken part in a Muslim marriage ceremony with a Pakistani man in his 30s in late 2011. She said the woman had become pregnant "almost immediately" and had given birth to a son in the summer of 2012.
"A Muslim marriage, not recognised in this jurisdiction, was performed between them," said Mrs Justice Parker. "An anonymous informant had telephoned to state that the (woman's stepfather) had received £20,000 in consideration of the marriage."
She said six weeks earlier the man's application to stay in the UK following the expiry of a two-year student visa had been refused.
He had subsequently applied for "leave to remain on the grounds of his marriage". The judge said "immigration proceedings" were "as yet unresolved".
The judge concluded that the woman lacked the capacity to consent to sexual relations and lacked "sufficient understanding" to consent to marriage.
Mrs Justice Parker said the man was basing a claim to remain in the UK on his right to family life enshrined in the European Convention on Human Rights.
"The reality is that he is now relying on his marriage and fatherhood... in support of his claim to remain," said the judge. "So, the reality is that whatever his original motivation, (the woman) is being used."
She added: "(The man's) position is bound to be self- serving."
Mrs Justice Parker said the case had been about the woman - not her son. She was told that man wanted stay in England with the baby. She said plans for the little boy's care would need "rigorous evaluation".