It may also be an expensive one, as subsidies may have to be offered as an incentive - short-term contracts are not an attractive proposition when long-term assurances are needed for things such as leasing rolling stock.
The basic point is that although there are powerful arguments for awarding longer term contracts, so that the successful bidder has an incentive to spend serious money on the best kit, a healthy scepticism needs to be attached to forecasts of the health of the economy and of the relevant public service over a time period as long as three parliaments.
And recorders are appointed on three-year contracts, renewable by the Lord Chancellor, which some might think gives them an incentive to toe the government's line.
In cases like government contracts, where future costs are speculative, allowing prosecution based on underbidding provides a dangerous incentive for individuals to bring frivolous claims against innocent businesses.