A student was today ordered to be detained indefinitely in Broadmoor secure hospital for killing an arts expert who blogged as Professor Whitestick.
Dr Douglas Hutchinson, 60, had been a successful chemist until meningitis left him frail and with partial sight in 2000.
He became an arts expert and was well-known on the internet as a campaigner for arts access for sight-impaired people.
It was after a trip to the National Gallery in central London last November that he was spotted by psychotic German student Tim Sommer.
He followed him home to Goldhurst Terrace, West Hampstead, north London, and punched Dr Hutchinson to the ground in his front garden.
Horrified neighbours saw Sommer stamp on his head a dozen times, the Old Bailey heard.
Sommer later told police: "There was something about his eyes. He was the devil."
It later transpired that Sommer allegedly killed Fatma Bezohra, 46, in his home town of Wiesbaden, by beating her head with a table leg because "she was a witch".
He pleaded guilty to manslaughter on the grounds of diminished responsibility and was ordered to be detained indefinitely under the Mental Health Act.
He is now due to be sent to Germany to complete his sentence and for court proceedings on the murder of Ms Bezohra.
The Recorder of London Judge Brian Barker told Sommer: "You are a young man of intellect and you are also seriously ill."
The son of two plastic surgeons and described as a gifted student, Sommer was diagnosed as paranoid schizophrenic.
He had been admitted to mental hospital in Germany but discharged himself and stopped taking medication.
Dr Hutchinson died two weeks after the attack from massive head injuries.
Edward Brown, QC, prosecuting, told the court Dr Hutchinson had been killed in a "ferocious and unprovoked" attack.
Mr Brown added: "Mr Sommer said he was at that time an angel and that he thought Dr Hutchinson was the devil."
Dr Hutchinson was described by his family as "being a man of great intellect and as having been well respected".
Mr Brown said: "He was determined not to be a burden on society and sought to persuade others that they could live a fulfilling life despite their disadvantages."