A young St Albans father has been jailed for a year after throwing a single punch at a teenage boy which left him with serious brain injuries.

St Albans Crown Court was told the blow left Eli Stapleton unconscious and he ended up in Addenbrookes Hospital with multiple injuries.

Jailing 26-year-old office manager Gary Hardey yesterday (Tuesday), Judge John Plumstead told him the effects of that blow on his victim may be "long term and even lifelong".

The judge added: "It has changed his life. He still has the effects of the brain injury."

Hardey, of Lectern Lane, St Albans, pleaded guilty to a charge of inflicting grievous bodily harm on Mr Stapleton on the night of May 13 last year.

Sally Mealing McLeod, prosecuting, told the court how the defendant had been drinking with a friend in London Road, St Albans, when at around 10.30pm they decided to get into a taxi and instructed the driver to take them to a gym called Body Limits in Sutton Road, St Albans.

When the car eventually pulled up on the kerb, Mr Stapleton and some friends were walking on the pavement towards the vehicle.

The prosecutor said Hardey was sitting on the back seat of the taxi and his friend was in the front passenger seat.

The court heard there was "an exchange of words" between Mr Stapleton and the men in the taxi, prompting Hardey to get out.

She said "The defendant got out and punched Mr Stapleton once to the head which caused him to fall to the floor."

Hardey's friend pulled him away and they got back in the car, telling the driver to drive away.

Mr Stapleton was rushed by ambulance to the QEII Hospital in Welwyn Garden City before being transferred to Addenbrookes Hospital in Cambridge.

He was put in a neurosurgical unit and placed on a life support machine .

A CT scan showed he had multiple brain injuries and a drain had to be inserted.

The court was told Hardey had four previous convictions, but that in the last seven years he had turned his life around, settled down into a long term relationship and was a "hard-working family man with a young daughter".

Claire Fraser defending said: "He is absolutely distraught, not for the position he finds himself in but for the injury he has caused to Mr Stapleton."

Judge Plumstead told Hardey: "Someone has over-reacted with a single blow which has altered and possibly ruined a teenager's life."

The judge said a dispute had arisen that night between Hardey and Mr Stapleton.

"How it finished is why you are here today. You lashed out and punched a young man. I accept you had no idea of the harm that would result."

He jailed Hardey for 12 months.