Reports have emerged that the killer got down on one knee to propose to a female visitor in her 40s, who began writing to him two years ago.
Bellfield, 53, is currently serving a whole-life tariff in Durham’s HMP Frankland prison for murdering Marsha McDonnell, Amelie Delagrange and Milly Dowler.
Bellfield began his prison term 14 years ago when he was convicted of the murders of Ms McDonnell in 2003 and Ms Delagrange in 2004.
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While in prison, he was found guilty and given another life sentence after being tried for the murder of 13-year-old Milly Dowler, who had been abducted while walking home from school in Walton-on-Thames, Surrey, in 2002.
He is one of a handful of prisoners currently serving a whole-life term, meaning he will never be released
The Ministry of Justice has confirmed that Bellfield has officially asked for permission to marry.
A spokesman said: "An application has been received and is being considered in the usual way."
Bellfield will need the permission of Durham’s HMP Frankland’s governor for the marriage to go ahead.
Rules state that the prison governor can raise an objection to the facility being named on the notice of marriage as the place where the service is carried out.
The governor must discuss with the National Offender Management Service if there are concerns that any security risks cannot reasonably be overcome, or if there are concerns that either party is getting married under duress.