Two separate juries failed to agree verdicts, despite graphic CCTV footage showing Mr Whelan struggling with Joseph and numerous witnesses describing the savage knife attack.

When the second jury was discharged yesterday from the Old Bailey, Joseph changed his plea.

The prosecution accepted the new plea and is not seeking a third trial. 

Mr Whelan, 28, a hospitality agent, from Kentish Town, north London, died after being stabbed through the heart on the top deck of a number 43 bus in Holloway Road, north London, on July 29, 2005. His sisters, Teresa Ward and Dolores Whelan, said his death had changed their lives forever.

Mrs Ward said: “Anthony Joseph was an angry and vindictive man. He has tried to excuse his actions by claiming mental illness. He callously killed Richard for no reason. 

“Richard was a very private, quiet man with high values, who treated people with respect. He made the mistake of judging another by his own standards and paid with his life. Our lives have changed forever. We miss him every day.” Mr Whelan confronted Joseph – who had been drinking and taking drugs – after he threw chips at his girlfriend Kerry Barker, 38. But Joseph became “verbally and physically aggressive”, the court heard, and pulled out a knife. 

Philip Katz QC, defending, said Joseph was suffering from the onset of schizophrenia. 

Joseph was remanded in custody to Broadmoor. He will be sentenced on December 20.