It was from Lee's Hotel in Cork, now called the Munster Arms Hotel, that Michael Collins set off on his last journey. It would end 30 minutes later at Béal na Bláth.

The moment was immortalised in one of the Civil War's most iconic photographs, snatched by a local girl Agnes Hurley on her Box Brownie camera.

It showed Collins settling into the back of the Leyland Touring Car, the engine starting up, the usual crowd of people looking on.

Nobody realised that this was to be the last ever photograph of Michael Collins alive.

The last picture showing Michael Collins alive (Pic: National Museum of Ireland)

Why was Michael Collins in Cork in late August 1922?

Collins was in Cork to follow up on the army's success in capturing the city.

He also wanted to get down there to expose the IRA's secret money-raising operations being run from the city.

There has long been a belief that the main reason he was in Cork was to follow up on peace feelers put out by the anti-Treaty side. Is there much evidence for that?

There is very little evidence of any serious peace moves at that time. There were inconsequential encounters with mid-level IRA officers, but there is no record of contacts by or on behalf of Collins with the senior IRA officers.

Anyway, there was nothing to discuss; all Collins had to offer was unconditional surrender, there was no way to finesse that demand in peace talks.

One persistent claim over the decades has been that he was in Cork for a secret meeting with Eamon de Valera.

This is simply not true. Eamon de Valera was in Cork serving as a staff officer to the IRA Chief of Staff Liam Lynch.

But he was increasingly estranged from the IRA leadership, he believed the chance to succeed by force of arms was gone, and he wanted to return to politics.

Eamon de Valera

He got short shrift from the IRA leadership in Cork; he was on his way to Dublin, and his route took him through Béal na Bláth.

He arrived there with the senior IRA officer in Cork Liam Deasy to be told that Collins had just passed through, and that it was likely he would be ambushed if he were to pass back the same way.

It is at this point that de Valera is said to have remarked: "It would be a great pity if Collins were killed, as his place would probably be taken by a weaker man."

So he knew that morning in Béal na Bláth that an ambush was likely?

He knew, but there was nothing he could do about it. De Valera had at this point no standing with the IRA, no influence, and he knew it. He continued his journey to Dublin.

And Collins continued his tour of west Cork, oblivious to what was being planned behind him...

He did, and it was a strange journey, a nerve-jangling discordant mix of hard-headed military inspections, interspersed with back-slapping and emotional reunions with family and friends, buying rounds of drink, followed by adoring throngs of people wherever he stopped.

That reaction from the Cork people could have distracted him, dulled his legendary instinct for danger.

Michael Collins (Pic: National Library of Ireland)

He also mistakenly believed the war would end soon.

He was travelling in a convoy that was too large for the IRA to let go unchallenged, but at the same time too small to be decisive in an ambush.

So, what happened that evening of 22 August 1922?

Collins left Bandon at around 7pm, apparently to head back to Cork city, but the convoy went back the way it came, against all military wisdom.

The ambush nearly never happened.

The ambush that was planned, would have been formidable. Twenty-five men were on the laneways above the main road, there was a barricade, and a landmine of gelignite buried in the road.

It's a few hundred yards south of the Béal na Bláth crossroads - a shallow soggy valley with a stream flowing alongside the road, which bends twice before emerging at the crossroads.

A laneway runs parallel to, and slightly above, the main road. You add it all together and it made up a perfect combination of shooting gallery down onto the road, and lines of retreat.

But as evening approached, the officers in charge of the ambush concluded that the convoy was not returning that way, and the ambushers began to move away, leaving a handful of their number to cover the men dismantling the barricade.

A map of the ambush site at Béal na Bláth

Then the convoy appeared, and the few men left at the site opened fire.

Major General Emmet Dalton, in the car with Collins, ordered the driver of the car to "drive like hell!"

Collins overruled him: "No! Stop and we'll fight them!"

The men in the truck up ahead were already out on the road and returning fire.

The few IRA men in the laneway began moving towards the farm lanes they were going to use to retreat, and at this point they were most exposed to the soldiers on the road.

If the armoured car's machine gun had not jammed at that moment, it is likely that none of the IRA men on the laneway above would have been able to fire down at the road.

Collins saw the retreating IRA men, and stood up to get a better shot. He forgot that the IRA always had other men covering retreats. It was a bullet from one of those men that killed Collins.

Death was almost instantaneous.

A monument now marks the spot where Collins was killed

What was the reaction to his death?

The army moved quickly to stop any instant reprisals, but three unarmed Republicans in Dublin were abducted and murdered by men believed to be army officers.

The IRA reaction was far from exultant. IRA officer Tom Barry, who was a prisoner in Kilmainham by that time, watched a thousand republican prisoners spontaneously fall to their knees, to say a rosary for Collins.

De Valera was horrified. "There is no hope for it now," he said.

What was the government reaction?

This is where the real impact was felt. The great paradox of the war was that it was the civilians in the cabinet who were the bloodthirsty hardliners, not the fighting men like Collins and Mulcahy.

Even before Collins's death, the ministers wanted to proclaim the death penalty for anyone caught carrying weapons. Collins had resisted that call.

Now he was gone, and there was nothing to stop the cabinet getting what it wanted.

There was, at this time, what had to be the most chilling cabinet meeting ever in the history of this country, as the ministers contemplated what was ahead.

The Attorney General, Hugh Kennedy, put it up to the cabinet.

If you want to win this fight, he told them, governments facing similar crises in the past had only won by resorting to ruthless methods.

He told them what was needed was "prompt, effective, vigorous, and utterly ruthless action", with "no mistaken idea of humanity" let get in the way.

A commemoration ceremony will take place on Sunday to mark the 100th anniversary of the ambush and shooting dead of Michael Collins at Béal na Bláth in Co Cork. There will be live coverage of the commemoration on the RTÉ News Channel and on from 3pm