The decisions followed the deaths in March last year of his youngest son Andrew, 42, killed in Tanzania by a wounded buffalo, and his heir, Simon Master of Lovat, who died a few days later leaving debts of more than #7.4m.
Mr Foster said yesterday: ''After the sad happenings of the last 18 months, it has become necessary to sell off some parts of the estate in an attempt to reorganise and make the remaining part viable.
Mr Foster said Lord Lovat, the former Commando leader who died in March, aged 83, knew despite his failing health that parts of the estate had to be sold.
He would have known that this included the sale of the castle.
She continued: 'Our parents are also very concerned about our education.'They have tried many times speaking to Norma Young and getting her involved but yet she is not doing anything about it - she obviously doesn't care about the big problem.'So I decided to take matters into my own hand. 'We really need an official teacher such as our most recent teacher who was not only a great teacher but she made learning fun and exciting! Yours, sincerely Poppy Dennis'Poppy's mum Valerie Stuart-Orchard, 48, said that pupils need to have the same teacher day in and day out.
A frustrated 11-year-old girl has written directly to the Scottish Education Secretary to complain that she doesn't have a teacher.
His estates were forfeit and remained so until his son, Simon Fraser, won the lands back after a special Act of Parliament in 1784 allowed George III to restore them to the Frasers.
The Crown had been impressed by the efforts of the Fraser Highlanders in North America, particularly Quebec.
I would like to see the place go to one buyer but I just don't know what will happen.'' Mr Foster did not envisage any further sales.
Around 7000 acres and 60 houses will be left in the family.