Joanna Yeates's killer admitted his crime to a prison chaplain but was angry when told his confession would be passed on, a court has been told.
Salvation Army member Peter Brotherton told the jury he shook hands with Vincent Tabak before the defendant told him: "I have got something to tell you that is going to shock you."
Tabak, who admits manslaughter but denies murder, had been under 24-hour supervision at HMP Long Lartin, and was said to have told Mr Brotherton of his plan to plead guilty on February 8 - three weeks after his arrest.
Appearing in the witness box at Bristol Crown Court, Mr Brotherton said he decided he could not keep the information secret because Tabak was not religious.
Mr Brotherton, who has been visiting prisoners since 1975, said "there was a little bit of anger" in Tabak's voice after the chaplain said he would have to pass on the information. Tabak, was said to have made the confession on their third encounter.
"I'm not going to tell you anything else," Tabak was said to have told Mr Brotherton. When Tabak told him he had something that was going to "shock you", Mr Brotherton was said to have replied: "You tell me and we will see."
After Tabak said "I am going to change my plea", Mr Brotherton asked him: "Are you sorry what you have done?" Tabak was said to have replied: "Yes."
During cross-examination, Tabak's QC William Clegg claimed Mr Brotherton's comments differed from a statement he gave on February 16.
Mr Clegg said: "Let me suggest to you there was no suggestion of 'changing my plea'. 'I am going to plead guilty' - that's what he said. "You said 'What for?'. And he said 'For the crime I have done'."
When the barrister suggested some of his evidence on Tuesday was wrong, Mr Brotherton replied: "If that's what you say, I would agree with you."