A man who killed his 14-month-old son by punching him in the abdomen because he would not stop crying has been jailed for nine years.
Nathan Allen attacked Fletcher with both fists as he lay in his cot - and the toddler died from internal bleeding and damaged kidneys in January.
Allen, 27, had been left with the youngster for less than 30 minutes while his partner Danielle Hands, 19, went to see her family.
After the incident, Allen denied hurting his son, who the court said was suffering from nappy rash, but he admitted manslaughter at the start of his trial.
At the Old Bailey, the defendant, who was cleared by a jury of murder, had demonstrated hitting the child with his two clenched fists in a downward motion.
He said: "He was screaming and clinging to my arm. I hit him twice in the stomach. I didn't know what else to do.
"As soon as I'd done it, I realised it was wrong and I said 'Sorry, Fletcher' and I picked him up and cuddled him.
"I'm sorry for what I've done, I'm so sorry for what I did to him."
Allen, from Romford, Essex, added: "I just didn't know what to do, I was beside myself. I was frustrated with myself - my son was crying, I've never seen him cry like that.
"Fletcher was so happy and for me to see him like that, I felt like I was doing something wrong."
The Common Sergeant of London Judge Brian Barker told Allen: "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."
The judge said he did not fully accept Allen's explanation of events because the boy had extensive bruising on his face and abdomen.
Richard Whittam QC, prosecuting, told the court that Allen lied to police, claiming the boy drowned in the bath.
Outside court, Detective Inspector Colin Welsh said: "I strongly believe that Nathan Allen first seriously assaulted his son in the weeks leading up to this incident, when Fletcher suffered two broken ribs.
"On January 6, 2011, a vicious attack took place during which this defenceless 14-month-old baby suffered another fractured rib, trauma to both kidneys, internal bleeding and numerous bruises to his body, head and face, including what can only be described as a sadistic bite to Fletcher's face.
"He then failed to call an ambulance and get Fletcher the immediate medical help he so desperately needed.
"I am pleased that today's sentence reflects the gravity of his actions."