They gave him nothing but care, love and put a roof over his head, but Timothy Crook repaid his kindly parents by bludgeoning them to death before dumping their bodies 150 miles away.

Yesterday 44-year-old Crook was told he was likely to spend the rest of his life in a secure psychiatric hospital after a jury at Bristol Crown Court ruled that he killed his parents.

The court heard how Crook, who has a history of psychiatric problems, savagely attacked his mother Elsie, 76, as she lay on her bed in the Swindon bungalow the couple shared with their son.

He struck his mother at least three times with a hammer at their Thames Avenue home on the Greenmeadow estate – once as she lay bleeding to death on the floor.

She and her husband Robert, 83, were also strangled by Crook before he loaded his parents' bodies into his father's Nissan Micra and drove them to Lincoln.

The callous killer then dragged the bodies underneath wheelie bins in the garden of a home he owned in Foxglove Way along with a suitcase he had packed with their clothes.

The double murder was the chilling culmination of years of erratic, aggressive behaviour from Crook, a jobless, friendless loner who took all of his frustrations out on his parents.

During the trial Crook was ruled unfit to plead due to mental illness and appeared in court via video link from Rampton Hospital, where psychiatrists diagnosed him as suffering from a delusional disorder.

He remained motionless as the jury – who had been asked to decide whether Crook had killed his parents – took just 45 minutes to unanimously agree that he had.

The court was told that Crook moved in with his parents in 2003 after being released from a psychiatric hospital in Lincoln, where he had previously worked for the RAF.

In his increasingly paranoid and delusional state, Crook subjected his parents to intimidation and abuse over five years.

It was perhaps an argument over the state of the bathroom which tipped him over the edge into a murderous rage.

In his increasingly paranoid state, he ripped out the bathroom and insisted on replacing it himself, causing tension in the household.

Mr Crook was last seen buying his newspaper from the local shop on the morning of Saturday, July 7, 2007. Police believe the popular elderly couple were killed at some point during the Saturday and taken to Lincoln overnight.

Mr and Mrs Crook were reported missing to police on Wednesday, July 11 by friends who were concerned that they had failed to show up to a tea dance they ran.

When police visited the house and spoke to Crook they found no evidence of a disturbance. Crook claimed that his parents had gone to Lincoln to arrange to sell his house and he was concerned that they had not returned.

The bodies of Mr and Mrs Crook were found on July 11 by a Lincolnshire Police officer who had been asked to check the house by Wiltshire Police.

Forensic examinations of the bedroom in Swindon showed that some cleaning work had been done but spatters of Mrs Crook's blood were found all over the room.

Bin bags were also found in the house with a bloodstained duvet cover and clothing saturated in blood that the prosecution say was worn by Crook.

There were no witnesses who had seen the Micra on its journey between Swindon and Lincoln or had heard or seen anything at either property. Crook drove the Micra and left it at Newark railway station where he boarded a train to Peterborough and where his movements were captured on CCTV.

After arriving in Peterborough, he wandered around the town before getting on a train to London King's Cross, from where he went to Paddington and on to Swindon, arriving at about 3pm on the Sunday.

After the verdict Crook's sister Janice Lawrence, 52, of Swindon paid tribute to her parents. She said: "My mother and father were wonderful people, amazingly supportive parents and a devoted couple who adored their grandchildren and were loved by the whole family.

"They were known by many people in the Greenmeadow area and the dancing community who valued their friendship. We are all desperately missing them and to have been murdered in such a callous way by their own son is beyond everyone's comprehension.

"Whatever drove Timothy to do this, we will never know.

"I can never forgive my brother for murdering my parents and the devastation this has caused to me and my family."

It emerged yesterday that an independent inquiry had been commissioned by the East Midlands and South West strategic health authorities into the care Crook received at Lincoln and Swindon.