Bodyworn footage showed his father, then 83, with blood over his face and clothing.
He told the police officer: “I’m glad to see you, he’d have killed me.”
Griffin pleaded guilty to the two charges, with the charge of threats to damage property, relating to threats he made to burn down the neighbours’ house the day before, the court heard.
Prosecutor Andrew Scott said the victim suffered a fractured nose and bruising to a number of parts of his body, as well as losing a gold tooth, in the attack – telling the court: “It was gratuitous. It was degrading.”
In a statement read to the court, Mr Griffin senior said: “I’m still fearful of contact from Ian if he gets released and I do not want any contact with him.”
Scott said Griffin was convicted in France in 2014 of carrying out what was described as a “frenzied attack” on his fiancee Legg, who suffered 100 blows to her head, face and body and was found in the bath of their hotel room.
The defendant fled to Cheshire, where he was found in woodlands near Warrington before being extradited to France.
The court was told Griffin, who was in a wheelchair, was released after making an appeal on medical grounds.
He claimed on the day of his father’s assault he had taken two tablets of medication, for his legs, and had four pints and it came after a period of six to eight weeks in which he had been trying to protect his parents from men who wanted to blackmail his father.
He said: “I’m dreadfully sorry about what happened, of course I am, he’s my dad. I had a total meltdown.”
His mother Janet Griffin was called to give evidence in his defence and told the court: “He is a very good son.”
When asked about the men who he claimed were blackmailing her husband, she said: “My memory’s terrible.”
Judge David Swinnerton, who ruled Griffin was a dangerous offender, sentenced him to five years in custody with an extended licence period of a year.
He also issued restraining orders preventing him from contacting his father and his two neighbours for an indefinite period.