Two Cold War missile sites readied for use when the world came to the brink of nuclear war during the Cuban missile crisis have been given listed status.
The Thor missile site at the former RAF North Luffenham, Rutland, has been given a Grade II* listing, while the site at former RAF Harrington, Northamptonshire, has been listed at Grade II as a reminder of the "knife-edge moment in history".
The two sites are the most intact examples of Thor missile bases in England, with concrete launch pads and blast walls still remaining, along with mounting bolts for the platforms that would raise the missiles into a vertical firing position.
The Government made the announcement that the sites were being protected on the 50th anniversary of the Cuban missile crisis, which saw the two bases put on alert and their Thor missiles readied for a possible launch on the Soviet Union.
The listing, which recognises the two sites' architectural and historic importance, comes on the advice of English Heritage and is part of an ongoing project to ensure the best Cold War structures are preserved.
A total of 60 Thor missiles, developed by the US, were deployed at 20 sites in the east of England from 1958 under the codename "Project Emily".
They were manned by the RAF, but their warheads remained under US control, and the decision to launch them would have been made jointly by the two countries.
RAF North Luffenham is now St George's Barracks, while RAF Harrington is now mainly farmland.
Dr Simon Thurley, chief executive of English Heritage, said: "The remains of the Cold War are fading from view faster than those of the world wars.
"Our Cold War heritage is a complicated and not always easily loved collection of concrete bunkers and silos. But they are the castles and forts of the second half of the 20th century and we want to ensure that the best examples survive.
"These two missile sites are among the few physical reminders in this country of the Cuban missile crisis, a moment when the entire world held its breath.
"They deserve to be protected to remind present and future generations of this knife-edge moment in history."
Heritage Minister Ed Vaizey said: "Our Cold War heritage is often overlooked but it is an important reminder of a point in history and is worthy of protection.
"Listing these two missile sites is particularly poignant on the 50th anniversary of the Cuban missile crisis and serves as a very physical reminder of an uncertain and tense period where the world feared a nuclear war."
The crisis, in October 1962, saw the Soviet Union and the US on the brink of nuclear conflict after the Soviets sited armed nuclear weapons in Cuba.
Following 13 days in which the world held its breath, a deal was struck in which the Soviets would remove the weapons and America would not invade Cuba.
English Heritage is holding a series of events to mark the 50th anniversary, including a programme of films, tours, talks and a photographic exhibition at the York Cold War bunker, and tours of secret tunnels beneath Dover Castle which would have housed government and military officials in the event of a nuclear attack.