Britain has operated a “continuous, at sea deterrent” since the deployment of the Polaris system in 1968, and its rationale was very much linked to the Cold War context of the time. Because the adversary was the Soviet Union, basing missiles on land was seen as being vulnerable to “barrage” attack and pre-emptive destruction on the ground. The previous reliance on the RAF to deliver the deterrent was questioned due to improved Soviet Air Defences. The deployment of an Anti Ballistic Missile system around Moscow (Galosh) in the late 1960s also meant that only a Manoeuvrable Re-Entry Vehicle (MARV) on top of a ballistic missile could meet the UK’s stated policy of holding the Soviet capital at risk, the so called “Moscow criterion”. The result was a policy of basing the deterrent at sea where it is hidden, undetectable, invulnerable and mobile – which also increases its range. The choice of weapon – a submarine launched ballistic missile (SLBM) also gives greater range, assured penetration to the target and greater accuracy. Importantly it also gives commonality with the US Navy as the Trident missiles are bought from and serviced by the US. Whether the UK needs or can afford such an elaborate system for its nuclear deterrent is at the heart of the current debate. Nick Clegg calls Trident a “Cold War” weapon and questions whether Britain needs such a capable and expensive system. For the Lib Dems a cheaper option might be to return nuclear weapons to the RAF, who operated their own “sub-strategic” air based systems until 1998, or to equip the new F35 Joint Strike Fighters with nuclear missiles and operate them from the Royal Navy’s two new Aircraft carriers. A third alternative would be to build three or four more Astute nuclear powered submarines and to equip their tomahawk cruise missiles with nuclear warheads. Any of these options would be less capable than a straight Trident replacement. They would lack the range of the Trident system which is currently 7000 miles, would be more vulnerable to air defences and would blur the distinction between conventional strike systems and nuclear weapons, raising the spectre of an enemy mistaking a conventional attack as one containing a nuclear warhead. Any return to an air based deterrent would in theory be vulnerable to the airfield or carrier being attacked thus preventing an assured second strike capability. Conservative critics dismiss the Astute proposal as a “Tuppeny Trident”. It is even suggested by some critics that the Astute route might be more expensive than Trident as the submarines still need to be built and a new smaller warhead would have to be designed which would be very expensive, whereas the existing Trident missiles can still be used in the new submarines. Another alternative would be to build less than the four submarines that have been part of the force since the Polaris fleet of the 1960s. Four boats are regarded as necessary in order to guarantee that one is at sea at all times, but some argue that this isn’t necessary and that the boats could be put to sea at times of heightened tension. Others argue that Royal Navy Trident patrols could be coordinated with the French navy’s nuclear submarines so that there was always a “European” independent deterrent at sea.