We knew who they were the moment they approached us on the front line outside Aleppo. The Iranian Revolutionary Guards – no longer merely advisers but fighting troops alongside the Syrian army – emerged on the roadside in their grey-patterned camouflage fatigues, speaking good though not perfect Arabic but chatting happily in Persian when they knew we could understand them.

Why, they asked politely – they were courteous, but very suspicious in the first few minutes – were we filming this part of their line? A mortar exploded in a field to our right – sent over either by Isis or by Jabhat al-Nusra – and we had filmed its cloud of brown smoke as it drifted eastwards.

I told the Iranian commander, a tall, bespectacled and thoughtful man, that we were journalists. I got the impression that these men wanted to talk to us – which proved to be the case – but they were wary of us, as if we were dangerous aliens.

“When I heard that there was an English reporter asking for information in this area,” the man said, “I said to myself: ‘England is helping Isis and an English reporter is here asking for information’. The immediate thing in my mind was, ‘Where is this information going to go?’”

He apologised. We must not think he was hostile to us. “If you were in my place and you were fighting a harsh and brutal enemy like Isis in this location – and this is our front line – you would ask yourself this question: ‘What is the English reporter doing here – why should he be allowed here?’”

We explained that we were travelling with Syrian military personnel, and I showed the Iranian commander my press card – and he recognised my name and newspaper. There was much shaking of hands. The Independent was respected, he said. But he was still a very cautious man.

Iranian soldiers from the Revolutionary Guards march during a military parade in Tehran (Getty) (Getty Images)

Down the dun-coloured road in front of us, across the flat plains to the south-east where the Nusra and Isis lines still held against the Syrian advance, there was an awful lot of rifle fire and the sound of bullets whizzing past the buildings. Outgoing, the Iranians assured us – I’m not sure I believed them, suspecting the fire was coming from their enemies – but the shooting continued throughout our strangely existential conversation.

“One of the problems of this place is that the enemy is very close,” the Iranian said, pointing through the dust haze. “You see those two silos over there? Well, that’s where Nusra are sitting right now and watching us at this moment. Any time, a mortar can arrive, you will be dead – and I will feel responsible, because in the last few hours I have already lost one man and had another wounded.” We were not there to die, I told the man. Reporters have to live to tell their tale.

He grinned at us. “We make a distinction between death and martyrdom,” he said. “In my view, because you are here and seeking the truth and bringing that truth to the world, if you die here in this spot, you are a martyr.”

The comment was intended to be kind. He was allowing a non-Muslim to become a martyr – which I had no intention of becoming. I told him how I had the very same conversation during the 1980-88 Iran-Iraq war in a trench opposite Saddam’s front line. A soldier then had told me of the pleasure he would experience in dying for Islam and I had told him it was my intention to live, that death held no joys for me. Never the twain shall meet, I said to myself.

The Iranian officer – and seven others had gathered round him in the hot afternoon, the crack and zip of bullets still breaking up our conversation – insisted that “to fight in the way of justice is martyrdom”. But then a team of Iranian military IT men arrived, serious, courteous, and wanted to look at our camera. They looked at the pictures of the mortar explosion and concluded that we were telling the truth – we were not spies. They were frightened that we had filmed their own strategic locations.

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Then another younger man arrived, bearded but smiling broadly. “This is not the right place for you to be,” he said. “If you want to show the truth of what is happening, you should go to the north of Aleppo and you should see villages and how they’ve been destroyed and how those who rejected the rule of al-Nusra were treated. They have lost everything – their homes have been smashed – and even if the war was to end now, the clean-up and preparations to rebuild will take at least a decade. That’s how badly damaged everything is.”

I realised at that moment that this young man must have fought to retake the Shia villages of Nubl and Zahra with other Revolutionary Guard forces three weeks earlier. “You should understand the kind of suffering these people have gone through – that’s what you should be writing about,” he said. He looked at us to see if we understood, and I suspect that for him this was a holy as well as a military mission – which may not be quite the way to win a war. But there they were, the Iranians in Syria chatting away to us on the battlefield – the “real thing”, as journalists like to say – and we took our leave.

“We would like you to write the truth about this place,” the commander said. “And I’m sorry we can’t allow you to see our lines.” There were more smiles from yet more Iranians who had turned up on motor cycles and in Toyotas. And then the commander went to his vehicle and came back with a large box of Arab sweets and handed them to us. How very Iranian of him. England supports Isis, it seems, but he was ready to feed the English reporter on his front line. But please, no more pictures.