Insurgents are actively seeking to bring down one of the eight Chinooks operating in Afghanistan, which routinely carry more than 40 armed troops, in the hope it will weaken Britain's resolve to continue the campaign in Helmand.
In the last fortnight coalition forces have destroyed four anti-aircraft guns mounted on trucks averting a potential disaster.
Intelligence sources suggest that the Taliban's surface-to-air missiles have been made redundant by sophisticated jamming systems fitted to every British aircraft.
The insurgents have now resorted to the tactic of using AAA (anti-aircraft artillery) that was highly successful during Soviet occupation and are actively seeking to buy the weapons.
Using a twin barrelled 14.5mm cannons mounted on the back of a truck the Taliban would easily be able to destroy one of the eight slow moving Chinook helicopters operating in Afghanistan.
An operational helicopter commander said "any British helicopter" would be a high priority target for them but "a Chinook would be a great coup, a bonanza".
"We have been extremely lucky so far with a mixture of tactics and a combination of good risk assessment," he added.
"But as something that keeps me awake at night the loss of a Chinook would be the most recurring nightmare."
Every Chinook flight is always escorted by Apache attack helicopters as a further layer of security.
Within the space of 12 hours local villager reported two ZPU-1s (anti-aircraft guns) mounted on the back of pick-ups trucks were destroyed by US aircraft in the Nad-e-Ali district close to the town of Lashkar Gah where the British brigade headquarters is based and is frequently visited by Chinooks, often carrying VIPs.
The weapons were loaded and ready to fire in an area which has been a focus of heavy fighting between British forces and the Taliban in recent months.
A few days later the deadly twin-barrelled ZPU-2 model appeared on April 25 and was destroyed followed a day later by another ZPU-2 towed by a tractor that was taken out by Hellfire missiles fired from a Reaper drone.
The Taliban almost had a "spectacular" success when they hit a British Chinook which was carrying Gulab Mangal, the governor of Helmand, with AAA hidden in a wadi dry river bed. The pilot, Flt Lt Alex Duncan was awarded the Distinguished Flying Cross for landing the aircraft safely after a round punched a large hole in a rotor and damaged the hydraulics.
As all four weapons were destroyed it has been difficult for forensic analysis to be carried out on their origins. But there is some intelligence that suggests the guns were of Chinese origin and might have been bought from arms dealers in Iran and slipped across established smuggling routes through its border into Afghanistan.
There is confirmed intelligence that Taliban have been in the market for AAA weapons for the last year and could have purchased the weapons from Hezbollah, Pakistan or even China. The insurgent's treasury has been substantially boosted by the opium trade that is said to raise £40 million for fighting.
"The destruction of this anti-aircraft weapon without a doubt saved the lives of Afghan and Coalition forces," said a US military spokesman.
Helicopters are critical in covering the vast distances in Helmand to deliver supplies, troops and medical evacuation.
Originally produced by the Soviet Union immediately after the Second World War, the single barrelled ZPU-1 and double barrelled ZPU-2 machine guns were feared by US helicopter pilots in the Vietnam War.