Lord of The Rings is a box-office winner

The signed letter, written to a fan in September 1955, also revealed the setting of one of the kingdoms in the book.

Tolkien wrote: "I went for a brief holiday to Gondor (or in modern terms Venice) which only served to reveal my tiredness to the full and not to relieve it.

"Since my return I have let the days slip. Not to the detriment of Vol III!

"That was out of my hands some time ago... in the end much has had to be jettisoned, including the facsimiles of the Book Of Mazarbul and the index of names (with translation).

'Worthy ending'

"Such as it is, another 300 pages of narrative and about 100 of additional matter should appear soon.

"I will not relieve your anxiety about the fate of the various characters, but I hope the ending will not seem unworthy.

The letter referred to a holiday "in Gondor"

"I have not myself any doubt that things went just so, but that does not say that my attempt to record them is successful.

"The problems of presentment with so many centres of sympathy and attention were considerable."

Richard Westwood-Brookes, of auctioneers Dominic Winter, said: "I advised the vendor that a sale around about now would be very good timing because of the film.

"But there is always great interest in Tolkien items because there is a whole generation of people, who have got a lot of money, who grew up grew up with Tolkien's books."