A secret memo from January 1995 shows how a former Defence Secretary once considered making Russia an "associate member" of NATO.
The document, from Malcolm Rifkind's time in charge of the department, pre-dates a Chequers summit on foreign policy and suggests a potential relationship change between Central Europe and Russia for the first time since the Cold War.
The note was released among a tranche of declassified documents at the National Archives at Kew.
It said that making Russia a full NATO member would "always be impossible", but that a "new category of associate member" could allow meeting attendance without granting a collective defence guarantee.
An Article V guarantee, a cornerstone of the alliance, operates on the premise that an attack on one NATO ally is an attack on all member nations.
At the time, such a commitment could have complicated the process of sending forces to the corners of Europe to fight on Russia's borders - the memo read.
Aides agreed to keep the suggestion confidential ahead of the Chequers summit. Minutes taken from the talks read:
"At the extreme, some were even contemplating including Russia in NATO.
"That was farcical and should not be on our agenda."
The account also states that former Chancellor of the Exchequer Ken Clarke, "was cautious about (NATO) expansion", whilst then Prime Minister John Major described the UK as "too much of a team player".
Mr Rifkind agreed at Chequers that Russia should not become a full NATO member, but stressed the need to make it "a more normal member of our western family", or risk it reverting to authoritarianism.
NATO, the North Atlantic Treaty Organisation, recently marked its 70th anniversary.
It was formed in 1949 to deter the expansion of the Soviet Union and secure peace in Europe, in response to the developing Cold War. The alliance currently has 29 member countries, although Russia is not among them.
Cover image: Moscow skyline (Picture: PA).