London - Ex-US Marine Ernest Langdon pulls a pin and throws a small black object onto the ground. But it doesn't explode. Instead, the robot rights itself and swiftly scuttles away, feeding infrared video back to a small radio control screen.
Unmanned drones have become an almost ubiquitous presence on the battlefield for US and other high-tech forces.
But the market for remote controlled vehicles is evolving from the sometimes multi-tonne craft that patrol the skies over Afghanistan or Yemen, carrying out reconnaissance and targeted strikes, to tiny robots that police and even film companies can use.
The top end of the market continues to be dominated by US companies such as Lockheed Martin, Northrop Grumman and General Atomics, formerly a division of General Dynamics and creator of the Predator and Reaper drones. Other major defence firms such as BAE Systems are pushing forward with next-generation drones with stealth and other features.
Smaller companies are increasingly redefining the industry, however.
Drones on display at this week's DSEI defence fair at London's Excel exhibition centre include undersea robots that can act as mini submarines or simply drive along the surface of the seabed to clear mines or conduct reconnaissance.
Remote control "quadrocopters" with four or more rotors can be launched from backpacks.
Even conventional military vehicles are becoming increasingly robotised. The stand of US truck manufacturer Oshkosh showcases a picture of a convoy of military trucks it says are being entirely remote-controlled.
Critics of the use of drones controlled remotely argue that they make warfare too clinical and easy, and too often end up killing innocent people. Advocates say the reality is that a drone removes the three "D"s - "difficult, dull and dangerous" - making it increasingly difficult to justify deploying human beings in certain situations.
US-based firm ReconRobotics say their products, robots designed to help soldiers or police look inside a building before they storm it or under a vehicle to detect a bomb, are already saving lives.
"It gives you eyes inside a room before you go there," said Langdon, a former Marine Corps sergeant and now director of US and international military programmes for the company.
"Maybe that means you see there are children in a room so you don't throw a grenade. Maybe it means you find an IED [improvised explosive device]."
The company says it has sold more than 4 000 of its 540g Throwbots and slightly larger Recon Scouts. More than half have been sold to the US military, the vast majority for immediate use in Afghanistan, but police departments are also major buyers. Each unit retails for around $16 000.
In March last year, French counterterrorism commandos used two Recon Scout robots before they stormed a house in Toulouse where a gunman, suspected of shooting three French soldiers, three children and another adult, was hiding.
Operating almost silently inside the house, the robots were able to locate 23-year-old Mohammed Merah in the bathroom. He was shot and killed after a 30-hour siege.
ReconRobotics' next product will be a small tethered flying quadrocopter able to fit in an infantryman's pouch, allowing the operator to silently check out higher floors, Langdon said.
Nearby, Estonia's Eli Airborne Solutions is demonstrating its own smaller quadrocopter, already in service with Estonia's border guard and hoping for exports to Latin America and other emerging markets.
Until recently, Israeli firms - early starters in the sector and less encumbered by export regulations than their US and European counterparts - had the edge in the smaller drone market. Now, industry insiders say, even that is opening up.
Colena - a small British company based in a business park in South Shields, north-east England - say the main users of their five-rotored radio-controlled copter have been film companies.
At £2 000 a day, hiring one of their drones and an operator costs roughly the same as hiring a helicopter and crew for a single hour. They say their system has been used in filming for the BBC's Top Gear programme as well as HBO's Game of Thrones.
They hope they too can crack the lucrative military market, using similar systems to offer views over battlefields and facial recognition software to scan crowds at public events.
"At both ends of the industry, you're seeing phenomenal growth," said Douglas Barrie, air power analyst at London's International Institute for Strategic Studies.
"You see it at the end where you have small robots to be thrown through a window and you see it at the higher end where you have large, expensive drones with artificial intelligence designed to operate for hours or even days at a time."