The Law Lords are to hear an appeal brought by one of the UK's most infamous spies, George Blake.
Blake is fighting to have a court order lifted that freezes the profits of his recent autobiography.
After considering the matter in private, Lords Nicholls, Hutton and Hobhouse have now granted leave for appeal against the order, which was imposed by the Court of Appeal in December 1997.
Blake, a member of the Secret Intelligence Service (SIS) from 1941 to 1961, was jailed for 42 years in 1961 after pleading guilty to spying for the Russians.
However, in 1966 he escaped from Wormwood Scrubs prison and fled to Russia, where he has lived ever since.
There is no likelihood that he will ever return to the UK, where he would probably have to serve the rest of his prison sentence.
The legal row is over the proceeds of a u100,000 deal under which his autobiography, No Other Choice, was published in 1990.
In the High Court on 19 April 1997, Vice Chancellor Sir Richard Scott dismissed moves by the Attorney General to prevent Blake receiving profits from the book, which was published in the UK by Jonathan Cape.
Sir Richard ruled that the insistence of the Crown on a lifelong duty of fidelity for members of the security service represented an interference with the rights of free expression.
He took the view that a duty to refrain from disclosing information that was neither secret nor confidential was not necessary in the national interest in a democratic society, even in the case of someone like Blake.
However, in a decision that has wide implications for other security service personnel who wish to write autobiographies, the Court of Appeal reversed Sir Richard's ruling.
Its reversal was based on the provisions of the 1995 Proceeds of Crime Act, which is aimed at preventing criminals from retaining proceeds resulting from an offence that they have committed.
In argument likely to be repeated before the Law Lords, the Attorney General, in fighting to prevent Blake getting the money, claimed that Blake had broken his trust with the SIS by writing the book.
The autobiography deals with his time with MI6 between 1947 and 1961, his arrest and conviction for spying in 1961, and his escape from prison and his subsequent life in Russia.
He further claims that Blake, now 74 years old, still owes a fiduciary duty to the Crown and that this duty of trust to his former SIS employers surpasses any rights he may have to free speech.