The latest addition will allow Britain's 39 Squadron to fly multiple Reaper aircraft at any one time over Afghanistan. The Reaper is manufactured by General Atomics Aeronautical Systems of San Diego.
In London, the Ministry of Defense said in a statement that 36 hours of video surveillance can now be delivered in support of troops every day, an 80 percent increase from 12 months ago.
"I have never felt more connected to the heart of the battle on the ground than when I'm flying the Reaper," said one pilot quoted by the Defense Management Web site.
"When you're speaking to a soldier on the ground for hours at a time, night after night -- looking around every corner for him, scanning every tree line and reacting every time his guys take fire -- you feel like you really are fighting alongside him."
Reaper has been supporting ground forces in Afghanistan since 2007 and has flown more than 13,000 hours in direct support of operations. With an operational ceiling of 50,000 feet and a maximum internal payload of 800 pounds, the Reaper provides commanders with a constant "eye in the sky" that can "seek out and track insurgent activity around patrols, search for potential explosives and provide an armed response if required," said a Defense Management report.
British Defense Secretary Liam Fox said the Reaper was crucial to the air force's operation in combat zones.
"The arrival of this new aircraft demonstrates out ongoing commitment to ensuring that our troops on the front line get all the equipment that they need," he said. "The Reaper continues to play a vital part in our air power capability in Afghanistan and there is no doubt that this cutting-edge technology is saving lives."
The aircraft, which has a combat function, is able to launch Hellfire missiles and laser guided bombs.
The United Kingdom requested the sale of an additional 10 Reapers in January 2008. In August the same year Italy requested a batch of four with ground stations.
The Reaper's delivery comes amid growing concerns that stiff regulations should be applied for the use of drones.
Research is under way to enable unmanned vehicles to work in collaborative swarms, ensuring each machine selects a different target. This though has fanned fears that such strikes along the borders of Afghanistan and Pakistan could spike already alarming death tolls.