On learning the news of Beadman’s death, Kayleigh’s father, Martin Whitby, posted his reaction on social media.
Writing on Facebook, he said: “Best news ever… the ******* that killed my daughter is dead.
“Hope the ******* rots in hell.”
The cause or circumstances around the death have not been revealed.
A Prison Service spokesperson said: “HMP Wakefield prisoner Stephen Beadman died in hospital on April 8.
“The Prisons and Probation Ombudsman has been informed.”
They added: “The Prison Service cannot confirm the cause of death, which is rightly a matter for the coroner.”
Kayleigh had tried to escape Beadman’s clutches when he – and another man Luke Harlow – plied her with drink at a flat in Ibstock, Leicestershire.
But the schoolgirl was sexually assaulted by Harlow before trying to flee, at which point she was chased by Beadman, who raped and murdered her with a brick before dumping her body in a farmer’s field.
Kayleigh’s body was found five days later. She had to be identified using dental records.
Harlow was sentenced to 12 years imprisonment.