SAS believed to be on the ground in Afghanistan
Members of the Special Air Service are believed to be the British ground troops on operation in Afghanistan.
British defence minister Geoff Hoon says troops are on the ground but would not confirm their presence.
But intelligence magazine Eye Spy says the SAS has been working with MI6 and the CIA in Afghanistan.
Surveillance, identifying targets for air strikes, forging links with local communities and assisting the northern alliance with tactics are thought to have been among their main roles.
They're also believed to be installing miniature digital cameras alongside roads and mountain paths to collect intelligence.
Defence expert Mike Yardley said: "The SAS would be mainly deployed in three roles.
"The first is gathering intelligence on the Taliban and presumably also looking for Osama bin Laden.
"The second is acting as forward observation officers to target in laser guided weapons and pass on communications.
"The third is to act as some sort of snatch, destroy or killer group to attack bin Laden or his lieutenants in their lairs and we would expect them to be backed up by other forces for that role such as the US Rangers who we have already seen in action."
The SAS has four squadrons of around 50 highly skilled soldiers, each split into groups trained for different specialist roles. Only in major operations such as the Falklands War are entire squadrons deployed together, and the whole force is never put into action at once.
