Children's author Harry Horse 'stabbed his wife 30 times' as probe casts doubt on 'Romeo and Juliet suicide pact'

But it has now been revealed that the writer and artist stabbed his wheelchairbound wife 30 times before slashing himself to death.

A year-long investigation has indicated that 46-year-old Horse, a drug user prone to bouts of anger and depression, slaughtered his wife, Mandy, 39, who had multiple sclerosis.

Tragic: Mandy and Harry Horse on their wedding day in 1991. It was originally believed he killed his dying wife in a suicide pact

The assault was so violent that the knife broke and he continued with a second.

Horse  -  real name Richard Horne  -  then killed the couple's cat and dog before slashing himself 47 times. He bled to death.

After the couple were found in their home on the Shetland island of Burra in January last year, reports suggested Mrs Horne died from an overdose administered by her husband before he, too, took the painkillers.

But yesterday her mother admitted that for the last 16 months the true and dreadful nature of their deaths has been kept secret.

Grace Williamson, who lives with her husband, George, 61, on Burra, said: 'We have only been able to cope because they are both now beyond pain. Quite simply, he went mad.

Artist: Harry Horse worked as a cartoonist and a children's author

'We cling to the fact that they were in love and had 18 years together before their lives were ended by this moment of madness.'

Police, residents and the authorities in the Shetland Isles did not reveal how the couple died.

An investigation at the time established that no one else was involved in the deaths and the procurator fiscal decided a fatal accident inquiry would not serve the public interest.

A Northern Constabulary spokesman refused to comment yesterday.

But Peter Gillman, the journalist and author whose investigation revealed how the couple died, said: 'My wife, Leni, and I began by investigating what we believed was a poignant love story.

'We soon realised there was more to it. The records indicated they died from blood loss and not from drugs.'

The families of the couple believe Horse could not go on witnessing his wife's suffering and did try to end her life with painkillers. When this did not work, he flew into a frenzy.

Harry Horse was known for books such as Little Rabbit Runaway

It is understood the author, known to use ecstasy and cannabis, had taken a 'cocktail' of drugs. Witnesses said he was roaming the house hours before the killing, proclaiming: 'It's a wonderful night for a killing.'

Horse was best known for his children's book The Last Polar Bears and his work as a political cartoonist.

The Englishman moved to Edinburgh in 1978 and changed his name.

He was touring as a musician in Shetland when he met Mandy. According to friends, her ' stillness' was a counterpoint to his volatility.

The couple moved to the Shetlands in 2004 after she was diagnosed with an aggressive form of MS.

As her condition worsened, he became increasingly depressed.

Mr Gillman added: 'This tragic story turned out very differently from the one we anticipated.

'We were shocked and astounded, but we felt we had to see it through.'