"Dun Briste is one of those iconic and elusive summits. The two attempts prior to the ascent did not put me off — it rekindled the fire of enthusiasm to stand on top."
The sea stack off Downpatrick Head in County Mayo was part of the mainland until the 14th century.
It is believed St Patrick had founded a church on the headland.
According to local legends, when a pagan chieftain refused to convert to Christianity, St Patrick struck the earth with his crozier, causing a chunk of the headland to split off into the sea with the chieftain still on top.
A more likely version of events is that coastal erosion collapsed the cliff around the shard of rock in 1393, when locals had to be rescued from the separated chunk using ships' ropes.
However Miller — who runs adventure and climbing company Unique Ascent — voluntarily chose to undertake the extremely dangerous climb, and even filmed the dramatic ascent.
He and climbing partner Paulina Kaniszewska approached the sea stack in a dingy before beginning their precarious journey, equipped with full climbing gear.
A huge amount of research had gone into their adventure but fortunately calm sea conditions made the first part of the climb relatively straightforward.
But there was nothing easy about the climb and it posed numerous challenges to the pair, who can be heard panting with exhaustion in the footage.
Locals from nearby Ballycastle cheered Miller and Kaniszewska on from Downpatrick Head but unfortunately, rainfall prevented the latter from climbing more than 20m up the stack.
Miller managed to successfully reach the top and his GoPro footage shows him lying in relief on his back on the green grass as well as examining the ruins remaining there.
But arriving at the summit only meant Miller's journey was half way completed.
He explained: "Standing on top you are so focused on getting back down that there are no celebrations."
The daredevil returned to sea level by creating an anchor to absail down from, leaning back over the drop and walking down the rock face.
It was only when he and Kaniszewska were back at the bottom did relief flood over them.
Miller enthused: "Once we were back at sea level and in the boat then the first wave of celebration hits you and it is like a bomb going off in your head."
The brave pair were greeted by the locals who prepared well-deserved hot dinners, and nine-year-old Naoise O'Sullivan even baked chocolate-covered queen cakes.
And was it worth it? For thrill-seeking Miller, it certainly was.
He told MailOnline Travel: "For me no other activity comes close to exploratory sea stack climbing for the happy-to-be-alive feeling."
The stack has only been successfully climbed once before by UK climbers Mick Fowler, Nikki Duggan and Steve Sustad in 1990.
According to the Irish Independent, Mountaineering Ireland have confirmed this and Miller's as the only ascents, but says it is "open to correction" if a record of another can be produced.
The only other time in recent history people have visited the sea stack is when, in the 1980s, a small team of scientists were dropped on the summit by helicopter in order to investigate the ruins.
Dun Briste also attracts birdwatchers due to the birds that make nests in its stratified ledges.
