As Greene continued his attack, Isabeth struck the victim once with the hammer, leaving puncture wounds on his right hand, left forearm and right inner thigh with one strike.
Greene then delivered more punches, wrenched the keys from the ignition and threw them up the road before driving off.
The victim told police that the hammer used in the attack was covered in white powder.
When police located Greene's van the hammer, covered in white powder but with fresh blood on the head, was inside it.
Greene said in explanation that the whole incident was a blur because he went into a fit of rage.
Both men were remanded on bail for sentencing on May 9.
Judge Jane Farish told Isabeth: "Be prepared, you are more than likely to go to jail.''
