He had intended to carry out the deed with a bayonet but used it to shatter a glass table instead before explaining: “I couldn’t go through with it. I didn’t do any damage to the dog because I ain’t got that in me.”
But just hours later the 55-year-old had no qualms about stabbing Tina Billingham, his partner of 17 years, in the heart and liver with a sword stick.
Then the callous car dealer immediately started to put a complex cover story into action, driving the 54-year-old victim to her GP surgery and alleging she had stabbed herself.
The burly bully’s boorish behaviour had driven 5ft 4ins tall, eight stone Miss Billingham – whom friends said always put the needs of others first – into severe depression and at least one drug overdose, after which the defendant refused to call an ambulance.
He insisted: “She was still capable of doing that herself. It was up to her.”
He rang her son – both had children from earlier relationships – and told him to come round to check on her before leaving to live with one of his sons for the next five weeks.
Cooke had a fascination with swords, knives and bayonets and a habit of exploding into wild rages when he did not get his own way. It was a toxic mix that ended in murder.
He already had convictions for attacking two former partners - one for common assault in 1999 and another for section 47 ABH in 2009.
The short-tempered tyrant regularly went on wrecking sprees in the house he shared with his partner in Granville Road, Old Hill. On one occasion he hurled part of a dumbbell through a window.
On the day she died he had destroyed the house phone, smashed her mobile and thrown a toy box, which hit her before the dog intervened, biting both of them.
Her eldest son Harry, aged 30, explained: “When Ron was not in a good mood he shouted and acted aggressively. He would smash things; TVs, tables, ornaments. It would happen every few months.
“If mum didn’t keep the house clean he would shout at her, calling her scruffy and a tramp. He deliberately damaged things she liked such as her clothes and her leather three-piece suite.”
Younger son Jack told police: “Although mum put on a happy face she told me she didn’t want to live like this and didn’t want to have to slip out to see me.”
Her visits to the home shared by him and his partner were brief, he said. “She would only stay a few minutes in case Ron accused her of sleeping around.”
Cooke admitted checking the mileage on her car to confirm she had been where she said she had gone.
Jack continued: “It was a controlling relationship.
“Ron was in the habit of telling her what she could or could not do. He did not like her going out on her own. I never saw him hit her but I saw her with injuries.”
Cooke became increasingly irritated by the amount of time Miss Billingham spent at the home of an elderly uncle who suffered from dementia and hoarded property.
The address had to be cleared of many of these possessions to make it safe for the man to return after six months in hospital.
Cooke, who killed his partner with a sword stick taken from the uncle’s home, revealed: “I asked her not to get involved. I told her we did not need that at this time of our life but the responsibility fell on her.”
He even wrote her a letter, which was never delivered, outlining how this issue was doing ‘irreparable damage’ to their relationship.
They were driving to collect the uncle and take him to his home when Cooke stopped his van to launch the deadly attack, almost certainly near Old Hill railway station.
Slightly built Miss Billingham was an easy target for her violent partner who had beaten her up on a number of occasions before the murder.
Her sons saw blood coming from an ear after the couple argued behind closed doors during a caravan holiday, while her sister Mandy Collins found her with a black eye and bruised face following a bust up around four years ago.
The battered victim, who had kept the attack secret for a week, asked: ‘What have I done to deserve this?’
The same question was being asked by heartbroken friends and family as her partner started a life sentence behind bars.