Inside Top-Secret Drone Operation Against IS

Sky News has been given unprecedented access to the US and UK's drone programme which is being used to gather intelligence for an assault on the IS stronghold of Mosul.

I spent time at a top secret base that could be key to recapturing the Iraqi city that fell to the militants in 2014.

All I am allowed to say about the base is that it is in the middle of nowhere, a few hours' drive from the nearest commercial airport and surrounded by desert.

Around 4,000 troops are based here. Mainly American, but I saw Canadian, Italian and Danish forces too.

Six British military personnel make up the numbers.

On the far side of this unnamed base is a temporary hangar. Underneath are three RAF armed Reaper drones.

Remotely Piloted Air Systems - RPAS - in official military parlance. The UK has 10 of these aircraft.

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Fifty yards behind, is a large cabin - the Ground Control Station.

"Sensors active?" says the pilot inside.

"Acknowledged," replies the weapons officer sitting on his right.

The cabin is a mock-up of a fighter jet cockpit. Screens and controls face them.

In the centre, a feed of the drone's main camera. Their window into this remote world.

This is the centre of the UK and US secret drone operation against Islamic State.

We cannot report which country the base is in.

I was asked to say it was in "South West Asia". We settled on "somewhere in the Middle East".

From here it's 60 to 90 minutes flying time to northern Iraq and Syria. Once there, the drones can stay "on task" for up to 13 hours.

Relentlessly watching their prey. Monitoring every movement a high profile Islamic State target makes.

In the words of the American officer I speak to, "we are the unblinking eye".

He oversees both countries' drone operations here. He must remain nameless, of course.

"We are going to be on that target as long as the weather allows and as long as the mission allows.

In many cases there is more than one asset on that individual.

"You know when he's going to go to the bathroom, you know when he's going to go to eat, you know when he's going to go to prayer time.

"You know where he goes, his associates.

"That's all about building that picture so that we know and we can project when he's going and where he's going to be."

Once airborne, the crews at this base hand over to replica teams based thousands of miles away at Creech Air Force Base in the Nevada desert, or RAF Waddington in rural Lincolnshire.

Each day, those crews drive to work from their family homes, listen to the latest intelligence briefings, receive their tasks for that day, and then step into the war zone.

They might be ordered to watch a particular high-value target or provide close air support to the Kurdish Peshmerga or Iraqi Forces.

"We approach this in the same way we would if we were in an aircraft directly above the battle," one pilot tells me.

The only RAF officer sanctioned to speak without hiding is identity is Group Captain James Frampton.

He is a senior RAF commander based in the Middle East.

"An aircraft like this could be on station overhead for maybe 13 hours sometimes slightly longer than that," he said.

"It can loiter in an area for a considerable amount of time."

He and his colleagues are part of what is known as 'the kill chain'.

It's a dramatic phrase for a thorough legal process - the group of people who must decide whether an airstrike is legal or not.

The Reaper drones broadcast live pictures back to a command and control centre in Baghdad and a similar facility in another nameless Gulf country.

Gp Capt Frampton and his colleagues - lawyers amongst them - watch the feeds and make a collective judgement on each target.

The pilot can refuse to launch the missile if he or she doesn't believe the conditions are right.

A 'safe-area' nearby is identified so that the weapon can be steered away from the target right up to the very last moment.

It does happen, I'm told, but rarely.

Ominous and predatory they might be, but statistically the drones' main role is intelligence gathering.

Since British drone operations began, Reaper drones have flown 17,590 hours and released 369 weapons - approximately one every 49 hours.

The drones are most effective staying above a target and watching, for hours and days on end.

One pilot explained: "It's a long period of time, which means you can gather quite a lot of what is actually going on.

"Rather than just having a quick snapshot of what is going on on the ground, you can really analyse what has happened and what is happening."

A senior commander reveals to us that RAF drones flying above Iraq have recently noticed senior IS leaders fleeing the city of Mosul as they fear an assault on the city.

That assault is certainly in the planning and this drone operation is at the centre of that.

The fight against Islamic State won't be won from the air.

But the air campaign is punching a hole in their ranks, eliminating key personnel, without let up.