A retired teacher knocked his wife out with a dumbbell and then slit her throat in a 'mercy killing' at their £390,000 home because he couldn't cope with her dementia, a court heard. John Colin Bennett, 75, killed his wife Beatrice, 75, at their North Shropshire home after struggling to come to terms with her debilitating condition. His devoted wife of 55 years had been left unable to recognise her husband as a result of Alzheimer's disease and regularly called him a 'double' or an 'imposter'. John Colin Bennett, 75, killed his wife Beatrice, 75, at their £390,000 North Shropshire home (pictured) In May last year Mr Bennett decided he wanted to 'end her pain' and severely struck his wife with several blows to the head with a dumbbell fracturing her skull. He then cut her throat with a kitchen knife before calmly calling 999 and telling operators: 'I've done a terrible thing, I have murdered my wife.' The pensioner was detained in a psychiatric clinic under the Mental Health Act yesterday after previously admitting manslaughter at Stafford Crown Court. Judge Simon Tonking said: 'This wasn't a premeditated killing. It was, in part, an act which you believed to be one of mercy.' The court was told the happily married couple, both retired teachers, were completely devoted to one another but were unable to have children. They were described as a very 'private couple' who lived in Market Drayton, Shropshire, and relied on one another for almost everything. He then cut her throat with a kitchen knife before calmly calling 999 and telling operators: 'I've done a terrible thing, I have murdered my wife' The pair had a 'happy and active' retirement until Mrs Bennett, known as Trixi, began to show signs of dementia in 2011. Prosecutor Deborah Gould said: 'She was an enthusiastic bridge player and her condition first became noticeable whilst she was playing. 'Mr Bennett became plagued with fears about their future, he became depressed, unable to sleep and was on sleeping tablets. 'What undermined the world of this couple was age.' When he dialled 999 to hand himself in, he said: 'She has Alzheimer's. I hit her on the head to stun her. 'I couldn't see her suffer any more so I put an end to it. 'She didn't recognise me as her husband. I have had two years living with this stress.' Michael Duck QC, for the defence, said: 'That which emerges most strikingly is the depth of affection between husband and wife, the way they had supported each other as individuals for five and a half decades. 'On any view, a happy married life. He is contrite in the extreme. The pressures brought to bear on that particular day came together in a tragic few moments.' Speaking at the time of the death neighbours of the couple in the picturesque market town expressed shock at the news. Local resident Paul Dawson, 48, said: 'Trixie was very ill. I can't believe it was murder, he was probably trying to help her die. 'It's just not possible, somewhere like this. I'm just gob-smacked.' Another neighbour James Mullineaux, 68, a retired police officer, added: 'They were a well respected elderly couple just enjoying their lives together.'
John Colin Bennett, 75, killed his wife Beatrice, 75, at their £390,000 home . Retired teacher was struggling to cope with her dementia and care for her . He knocked wife out with a dumbbell and  slit her throat in a 'mercy killing'
Mr Bennett then calmly called police and said: 'I have murdered my wife'
He has been detained in a psychiatric clinic under the Mental Health Act .