Prasanna Arulchelvam, 34, was found with head injuries at a Costco store car park in the town in May 2013 and died 11 days later.

Michael McInerney, 33, of no fixed address, denied murder but the prosecution at Luton Crown Court accepted his guilty plea to manslaughter.

Two men were jailed in October for Mr Arulchelvam's manslaughter.

Mr Arulchelvam, known as Nick, came to England from Sri Lanka in 1998 and lived in Grandfield Avenue, Watford, with his wife Shayanthy, 30, and their young son.

He died on 6 June 2013 in St Mary's Hospital in London after being attacked outside the Hartspring Lane store.

Mr Arulchelvam suffered a fractured skull and other injuries and was found in the car park by passers-by.

Alternative charges

McInerney, who disappeared after the attack, was arrested in Corby in December and charged with murder after detectives appealed for information about him.

Appearing via a video link he pleaded not guilty to murder and not guilty to conspiracy to rob but guilty to alternative charges of manslaughter and conspiracy to steal.

Prosecutor John Price QC accepted both pleas.

‘Judge Richard Foster remanded McInerney in custody. He is likely to be sentenced within weeks.

In October, cousins Patrick and James O'Driscoll, aged 34 and 45 respectively, were handed sentences of 10-and-a-half years and seven-and-a-half years after pleading guilty to the manslaughter of Mr Aruchelvam.