On board an RAF spy mission over IS-occupied territory

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Media captionJonathan Beale reports from an RAF Sentinel and talks to crew carrying out surveillance missions over Iraq and Syria

It is now a year since MPs gave the RAF the green light to begin their bombing sorties over Iraq against the extremist group know as Islamic State.

Eight Tornado jets, based out of RAF Akrotiri in Cyprus, along with 10 Reaper unmanned drones, flying from an undisclosed Middle East airbase, have now carried out more than 1,300 combat sorties, including more than 300 air strikes.

It costs a lot to take out an IS fighter using so called precision weapons.

A total of 93 Brimstone missiles have been fired - each costing more than £100,000; 244 Paveway IV bombs have been dropped - each costing more than £20,000; along with 212 Hellfire missiles - each costing about £70,000.

With all that firepower, the Ministry of Defence (MOD) estimates it has killed around 330 Islamic State (IS) fighters. However it admits this is a rough approximation given that Britain has no boots on the ground to assess the strikes.

Some might raise eyebrows when the defence secretary claims no civilians have been killed in those airstrikes.

Image copyright PA
Image caption Combat troops are unlikely to replace Reaper drones in the fight against IS

But it is clear the coalition is taking far greater care to protect life than Islamic State. There is no moral equivalence.

So what's been the impact of those airstrikes so far in this war?

Britain's just one member of the US-led coalition, and its contribution is dwarfed by the US.

Nevertheless, Defence Secretary Michael Fallon insists the UK's contribution is the second largest and should not just be measured in airstrikes alone.

The RAF's also carrying out more than 30% of all the coalition's Intelligence Surveillance and Reconnaissance (ISR) missions. Not just over Iraq, but over Syria too.

Islamic State oil tankers

We joined such a mission, boarding a Sentinel spy plane at RAF Akrotiri to look down onto Syria and into the activities of IS.

Image caption The mission took the RAF along the border between Iraq and Syria

This small, modified executive jet bulges with powerful sensors and radar which can scan thousands of square miles.

On board three of the five crew peer into computer screens to analyse the information.

We were asked not to identify them for security reasons. Nor were we allowed to film or photograph their screens.

The Sentinel acts as a wide search-light sweeping huge tracts of land. Once it identifies anything of potential interest it can call in the spotlight - other aircraft, such as fighter jets or drones, fitted with cameras to take a closer look.

Flying high above the border between Iraq and Syria, one of the crew, "Mark", described what he was seeing on his screen.

To my untrained eye it looked like scratches. It was, in fact, hundreds of oil tankers queueing up at a refinery.

Mark followed the path of the trucks as they went across the border into Iraq.

Oil is one of the extremists' main sources of income. Acting on this intelligence though is not always easy.

Calling in air strikes could end up killing innocent civilians who may have been forced to drive the trucks.

Hitting oil refineries can also cause significant environmental damage. It underlines the problems of fighting a war from tens of thousands of feet in the air.

Complex Syria

The Sentinel crew say the picture they see in Iraq is much clearer than the one over Syria.

In Iraq they can follow the battle. The coalition claims that IS have already lost a quarter of the territory they once occupied.

Image caption The Sentinel's crew analyse images on their computer screens during the flight

I ask the commanding officer on board, Dave, whether he thinks the coalition is winning.

"I think if we look on the Iraqi side of the border, I would say 'yes'," he says.

But when it comes to Syria he admits "the picture is so confused there I don't think we could claim one way or the other at the moment".

And the situation in Syria is becoming more complex.

As we're flying near the border the crew identify a Russian military aircraft in Syrian airspace.

Moscow's been helping President Assad, and the increased Russian presence is another concern for the coalition.

No end in sight

The government's made clear it wants to expand Britain's military action to include targets in Syria as well as Iraq.

After all, IS pays little attention to the border.

Image copyright AP
Image caption Oil is a source of income for the so-called militant group Islamic State

Back on the ground, the RAF officer overseeing the whole operation, is waiting for the order.

Air Commodore Sammy Sampson believes the RAF's involvement in Syria "would have a real benefit to the coalition".

It is a political decision but he added: "I can guarantee we'll be ready as soon as they say."

But even if the RAF gets the green light to conduct airstrikes over Syria, it probably would not mean an increased military presence.

The RAF's frontline squadrons are already stretched. Nor is there an end in sight.

Sentinel crews, will be flying for months to come.

The defence secretary has just announced an extension of their mission into 2016.

Even though they believe they are making a difference one of the Sentinel crew answers his own question: "From the air are we going to solve the crises on the ground? Not at the moment- no."

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