[holding answer 22 January 2007]: “Mothballed” is not a term used by the MOD. I have interpreted it as referring to ships capable of being returned to operational service but for which there is no requirement to do so at this time. The only Royal Navy warship in this category is the aircraft carrier HMS Invincible.
Five other surface warships of destroyer/frigate size and above are at low or very low readiness; four of these are in refit. I am withholding further details as this could enable deductions to be made that could be prejudicial to national security.
The normal readiness cycle of every Royal Navy ship is comprised of a mixture of periods of lower readiness, typically for maintenance or refit, and periods of higher readiness. The extent to which costs are reduced during periods of lower readiness is not calculated separately and depends on a number of factors including the type of ship, the readiness state to which it is reduced, and the length of time spent at lower readiness.