Britain's special forces played an important role in Iraq, and in Libya. In Afghanistan, relentless special forces operations are killing 130 to 140 insurgent leaders every month, according to Lt Gen James Bucknall, the most senior British military figure in the country.

In an interview in the Guardian this week, the General hailed the actions of the SAS, suggesting they were the key to defeating the Taliban.

For years, the SAS and the SBS (the Special Boat Service) have been conducting night raids, often with US special forces, capturing and killing individuals identified - sometimes correctly, sometimes not - as Taliban commanders and their supporters.

It is hard to see what these killings are achieving. Assassinated "insurgent leaders" are being replaced by a younger generation even less likely to agree to reconciliation talks with the Taliban that the British top brass, notably chief of defence staff General Sir David Richards, have said they want, and the sooner the better.

While special forces set out on killing raids, conventional British troops engage in a battle for "hearts and minds". The jury is out over whether a carrot and stick approach is working in Helmand province, the base for the 9,500 or so British troops still in Afghanistan.

While most of these troops are busy mentoring and training Afghan forces, 500 British special forces soldiers are engaged in intense operations designed to kill as many Taliban commanders as possible. That such operations are of questionable legality is clear from the special (and secret) legal advice given to special forces, different to that given to the rest of the British armed forces.

Special forces will become increasingly important as conflict and warfare becomes more and more sophisticated, further and further away from the traditional world of set-piece battles and bombing campaigns. In Afghanistan, special forces are working increasingly closely with Britain's security and intelligence agencies, notably MI6. In future conflicts, special forces and spies will be joined by pilotless armed drones and cyber warriors in a new arsenal of key weapons systems.

This is not mere speculation. It is the considered view of most senior military officers. Yet Britain's special forces remain taboo, more so even than the activities of MI5 and MI6. Even the Ministry of Defence's D Notice Committee, which runs a system of voluntary self-censorship in cooperation with the media establishment, believes the official secrecy surrounding the activities of Britain's special forces should be relaxed.

Books may be written about the SAS, their operations may be described in the media, especially if they are accounts of apparently successful derring-do. But they remain officially secret. Officials and ministers do not comment on them, officially, to MPs, the media, or the public.

The SAS has one thing in common with the Trident submarine nuclear missile system. They are both officially taboo. One is relatively cheap to run and regarded as increasingly relevant. The other is costing tens of billions of pounds, and, senior military officers agree, increasingly irrelevant.