Kamal Stephenson, 25, of no fixed abode, approached his 61-year-old victim from behind on Thursday, April 19, 2018, and struck him with the iron pole at least three times, causing lacerations to the left side of his head and a fractured skull.
The incident happened on Kingsthorpe Grove, Northampton, where the 61-year-old man was working as a delivery driver.
He was taken to hospital following the offence where his injuries required surgery.
DC Chris Mann, said: “Kamal Stephenson attacked this man when his back was turned and subjected him to a nasty assault.
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“The outcome of this case could have been so much worse – the man could have died, and this is something which Stephenson seemed to completely disregard when he picked up that iron pole that day.
“I welcome the sentence handed out to Stephenson and hope he uses his time in prison to reflect on his actions in order to make better choices when he comes out.”