Beatrice , 75 , killed his wife John Colin Bennett , 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 .
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 .