7 December 2011 Last updated at 10:50 ET
Nathan Allen jailed for killing crying son Fletcher
Nathan Allen, 27, of Romford, told the Old Bailey jury he had hit Fletcher twice in the stomach in January as he lay in his cot because he was crying.
Allen was jailed for manslaughter, which he admitted at the start of the trial. He was cleared of murder.
Fletcher Allen died in an east London hospital in January from internal bleeding caused by an abdomen injury.
The jury heard the father had been alone with his son for half an hour when he attacked the child.
Fletcher's mother Danielle Hands, 19, had gone to visit her family leaving the toddler in his care.
Allen told the murder trial: "He was screaming and clinging to my arm.
"I hit him twice in the stomach. I didn't know what else to do."
He added that he realised his mistake immediately and said "sorry Fletcher".
Sentencing Allen, of Erith Crescent, the Common Sergeant of London Judge Brian Barker said he did not fully accept the killer's explanation as the child had had extensive bruising on his face and abdomen.
He said: "Your reaction was aggressive and extreme. You will have to live with your actions for the rest of your life.
"This was a terrible act and you must take responsibility for your actions."