When a raging fire gutted the interior of St Mel's Cathedral in Longford town on Christmas Day five years ago, some of the country's most priceless artefacts were burned to cinders, writes RTÉ Midlands Correspondent Ciaran Mullooly.

Included among the casualties was most of the 1,000-year-old wooden crozier of St Mel, the saint who gave his name to this neo-classical style building that had its foundation stone laid in 1840.

The devastating fire broke out in a chimney flue in the cathedral's dated heating system some time between midnight mass and 5am.

According to locals temperatures of up to 1,100C were recorded as the blaze spread dramatically from under a wooden floor to the height of the beams and into the roof over the church.

The damage was catastrophic. The cathedral roof was gone, the floor had collapsed into the crypt, and so intense was the heat that marble fittings had melted.

Paintings, tapestries and statues in that section were immediately destroyed - yet just a few yards from the centre of the blaze one remarkable painting was to survive the roaring fire - a work of art that was hanging on a wall at an altar in a side aisle remained relatively unscathed by the inferno all around it, and survived the fire largely intact.

The painting of the holy family was not a masterpiece of 18th or 19th Century art by any standards.

Of Italian origin, it arrived in St Mel's without much recognition for a little known European artist.

It stood alone in the left aisle of the cathedral - near the prayer offertory, where it became a favourite of the local churchgoers.

Ronan Moore, the senior project manager who has helped guide St Mel's back to full health these past five years, said it should have been one of the first canvasses to be set alight.

"We will never know how it survived," Ronan recalls in a new RTÉ documentary on the restoration of St Mel's to be aired on RTÉ One this Christmas.

"You can see it here just a few yards from some of the huge stone pillars and columns of the old church that were completely de-stablised by the searing heat of the fire - turning to dust and had to be replaced - yet the painting stayed intact above it all - while all around it was destroyed by those huge temperatures."

He doesn't use the word lightly but the former Bishop of Ardagh and Clonmacnoise, Dr Colm O'Reilly, has described the survival of the holy family painting to me as a miracle.

In the heart of a cold and miserable winter's evening in late November he told me he was going back into the building site that was St Mel's to get his first sight of the painting since its return to the now restored cathedral - restating his view that it was indeed miraculous that it should not have been completely destroyed while all around it perished on 25 December 2009.

Bishop Colm has now retired from active duty in the diocese of Ardagh and Clonmacnoise.

Aged 73 when the fire hit five years ago, he stood outside the burning church with a line of sympathisers on the morning of the fire - accepting handshakes and warm embraces from parishioners in the frosty conditions - like a man who had just lost a loved one in a sudden death.

"It was an horrendous experience to watch it dying before my eyes" he told me, "but one thing was clear even at that stage - it was impossible to save it".

Spending €30m on the renovation of a church in the heart of the country's worst ever recession was surely a decision he would never have taken - were it not for the insurance coverage that St Mel's enjoyed.

In our RTÉ documentary the former bishop admits that it would have been difficult to contemplate such a project ever being taken on at a time while one in five of the Longford population was out of work - yet he is adamant that, insurance coverage aside, he also held the responsibility of a modern generation to ensure that one of the most important heritage buildings of the midlands was restored.

The engineering struggle involved in bringing St Mel's back to its former glory was of titanic proportions.

At one stage locals feared the building core would actually collapse because of the initial damage caused by the fire.

The centrepiece of the battle was to try to replace 26 gigantic limestone pillars that lined the central aisles of the old cathedral.

"We had to painstakingly remove everyone of them and replace them with new stone" Ronan Moore recalls in the RTÉ documentary.

"This was one of the most challenging pieces of work I have ever had to take on - when one considers that each of those stone columns stood eight metres high, each one consisting of a decorative capital, a fillet stone, four intermediate drums and a base. Each weighed something like five tonnes."

The main building contractor, Gem Purcell, was challenged from the very beginning with this project. 

Given that there was no floor, no roof and that the 26 hand-carved limestone columns which supported the structure were effectively destroyed, they devised a system which allowed the delicate restoration work to proceed on three levels at the same time.

“We effectively had three building sites, one above the other,” Martin Healy, managing director of Gem says.

With no floor to support scaffolding a suspended steel support “bridge” was constructed which allowed one team to work on the roof while below the delicate task of replacing the columns continued alongside the “defrassing” of the fire-damaged internal masonry walls. 

Meanwhile, a concrete floor was laid while a team of very skilled plasterers set about recreating traditional cornices in the basement under the supervision of master plasterer George O'Malley.

Above all of this a new steel structure provided a temporary roof to keep the rain away and prevent further damage to the old cathedral.

The quarrying project required to rebuild St Mel's was mammoth.

Over 675 tonnes of native blue limestone from Leighlin, Co Carlow, have been installed – for the columns, the hand-carved window surrounds, pilasters, and for replacement corbels for the bell tower, which also sustained some damage.

To get this amount of limestone in the section sizes required, a staggering 10,400 tonnes had to be quarried. 

Ronan Moore's 'Grand Designs' project was not without its setbacks.

The death of the man overseeing the design of the cathedral's rebirth in the very early days of the re-construction was a huge blow - and one that , remarkably, mirrored a similar event in the timeline that led to the construction of the original building in the 1800s.

After meticulously planning the job the chief architect Dr Richard Hurley died suddenly in December 2011 - nearly two hundred years after Joseph B Keane the original architect had also passed away while St Mel's was being built the first time around. 

In the filming of our documentary on St Mel's restoration, there were days when the sheer scale of the carnage in the old building made it seem this austere old church could never be brought back to life, but what has emerged is a very different church in my eyes.

Gone is the old austere feel to the place - the very long cold aisles leading down to the altar where my father brought me to attend confessions on many's the cold and icy Christmas Eve in the 1980s.

It is replaced today with a building that has a very modern feel - a newly-designed sanctuary, very much embracing the congregation and much closer to them in a physical way.

It's not an accidental change of focus either.

Dr Colm O'Reilly speaks in our TV documentary of the need there was not to just renew the old building in Longford - but after all the sexual abuse scandals of 1990s and the difficulties faced - to renew the church itself with its people.

"We wanted to build a church that was a fitting and modern place for people to gather for prayer" he says, "but it goes far beyond that - let this be a symbol somehow of renewal of the entire church in Ireland - a new cathedral for a different time."

Next weekend the doors of St Mel's will re-open for mass services again for the first time in five years.

The interior of the building will indeed look very different to churchgoers.

For starters, the seats of over 200 people have been taken out, a development that tells its own story, yet the pride of a county in the midst of this crippling recession will be very much present, and people who have turned to their church for support and faith in some of the darkest days of the last decade will now be walking tall again as they rise up the steps under that famous portico and say - welcome back to St Mel’s.

The Longford phoenix has indeed risen from the flames again.

'The Longford Phoenix' - a Would You Believe special documentary - goes to air on RTÉ One on 30 December at 6.30pm