The author of best-selling book The Horse Whisperer was today said to be in a "positive frame of mind" after falling ill from eating poisonous mushrooms.

Nicholas Evans was staying with his wife, Charlotte, at her brother's estate in Scotland when he fell ill.

Mr Evans and his wife, along with her brother, Sir Alastair Gordon-Cumming, and his wife, Lady Louisa, were taken to Dr Gray's Hospital in Elgin after eating the toxic mushrooms.

All four were transferred to Aberdeen Royal Infirmary where they were given dialysis and other kidney treatment.

A statement released through Mr Evans' London-based representative AP Watt, said: "They have been given dialysis and other forms of treatment to support their kidney function and have responded well.

"A family friend who visited them this weekend said they were all walking about and were in a cheerful and positive frame of mind.

"They are all extremely grateful for the rapid and effective intervention provided by the National Health Service."

The party had cooked and eaten the mushrooms on Saturday August 23 after having picked them in local woodland.

They became ill the next day and on Bank Holiday Monday were admitted to hospital in Elgin, where it was established they had eaten a rare variety of mushroom called Cortinarius Speciosissimus.

This type of mushroom is highly toxic - the toxins attack the kidneys in particular.

Last Tuesday, Mr Evans and Sir Alastair were transferred to the renal unit at Aberdeen Royal Infirmary, and their wives were transferred there on Wednesday.

Mr Evans' best known work, The Horse Whisperer, was made into a hit film by Robert Redford in 1998.

The book has sold more than 15 million copies worldwide.