Civilian casualties could cost Western Allies the support of the Arab world, as air strikes on Libya continue. But despite its formiddable firepower, the RAF's Tornado Force is doing all it can to avoid them.

In Col Gaddafi's warped world, human shields offer a win-win. If flag-waving civilians surounding anti-aircraft batteries means the Allies don't attack them, he can boast the Libyan people have frightened away the crusaders.

And if civilians are killed, their deaths are bound to shake the resolve of the Arab world to support the West as it brings the Mad Dog of the desert to heel.

Faced with the presence of civilians in the target zone, Marham Tornado crews called off their mission and turned north for the long flight back to Norfolk.

'People think you are paid to fly planes. You are not,' said former Marham Tornado pilot John Peters.

'You are paid to make decisions at those vital moments. That's why it's so difficult to get through all the training and into a squadron.

'You are bound to the decision you take. Your whole career can be on the line in those 30 seconds.'

Mr Peters, who was shot down on active duty in the first Gulf War, before being held captive and tortured in Iraq, said: 'In today's world you have to be absolutely damn sure you don't play into (Gaddafi's) hands.

'Whether the intelligence comes from the aircrew or an external agency, they will do everything possible to make sure they don't kill civilians.'

He said it was not unusual for planes to return without having launched weapons, adding: 'I don't think people realise how many bombs are brought home.'

Last night defence experts said the presence of civilians in the target area could have been confirmed by the pilots themselves, or intelligence could have been gathered from UAVs (unmanned aerial vehicles), or sources on the ground.

These sources could include special forces operating within Libya, local spies passing on information or even television broadcasts.

Mike Gething, contributing editor, Jane's Air Desk, said he was '99pc certain' the decision to abort would have been based on intelligence sources on the ground.

This could have come from special forces operatives or even material gathered from television broadcasts, he said.

'There's only one way it could be known and that's eyeballs on the ground. Whose eyeballs and who they belong to, I couldn't tell you.'

Mr Gething said the jets would have been carrying Storm Shadow missiles capable of firing at range, meaning the pilots would not have had the opportunity to identify civilians themselves.

'The fact the mission was aborted is evidence of the care that the operational commanders are taking to avoid civilian casualties,' he added.

But Shashank Joshi, an associate fellow at the Royal United Services Institute, warned the caution over civilian casualties was likely to abate over time.

He said: 'The pattern is they realise they are militarily hobbled if they are too cautious. They get very frustrated and expand the mission. This is what happened in Kosovo.'