"Is this the first time you've climbed?" asks the man with the clipboard, appending a yellow sticker to the archbishop's raincoat.
It is. Now it's just after 7am and Archbishop Seán Brady, the first of St Patrick's successors to join the pilgrims on the Reek, we're told, looks north. The summit is far off and veiled by a light mist and a threatening sky.
"It would be untrue to say I'm a big walker," he says. "I'm a little apprehensive, but we'll see how it goes."
Early it may be but already up to 1,000 people have made the climb this morning. One of them is 20-something Stephen McGuinness, who left home in Co Roscommon at 2.30am for this, his second time at Croagh Patrick, and his first barefoot.
"And as you can see, my feet are cut to bits," he says, nodding downward to the black-and-red stumps where his feet used to be. "But sure I'll rest up when I get home."
Where the incline first reveals itself, a group of women have assembled to collect funds for an MRI scanner for Mayo. "Alright for water, lads? You've Lucozade? Sound."
They move soundlessly most of the time, with only the rhythmic crunch of boots on the surface and the thwacks of the light rain on plastic vying with the sound of the wind. By now a constant line of climbers can be traced along the hills, a caterpillar formation of three-legged pilgrims - the traditional two plus the ubiquitous hazel stick selling for €3 in the car park below - winding its way through the rain. All along the way, those coming down can't help but smirk at the lungless masses still making their way up the slopes.
Achievement is subjective among us, one's own sense of hardiness ever vulnerable to the overtaking manoeuvres of the barefooted we encounter. One man, barefoot and T-shirted, approaches us at speed, gliding over the jagged rocks with - yes - a boy on crutches fast on his darkened heels.
Ah, these stalwarts. You can only admire them. Unless, of course, you're a man, when you can only do your best to outpace them. And all the while modestly exhibiting your instinctive familiarity with the ways of a mountain you might, strictly speaking, never have set foot on.
Whatever about the climb, the descent on the mountain's loose rocks looks all the more difficult. Though there is always an easier route: by stretcher. "We've just been radioed about a woman with a locked knee," says a man from Mayo Mountain Rescue. Already this morning, they reunited a child with his anxious mother and arranged for a man with chest pains to be air-lifted to safety.
The 67-year-old Archbishop Brady, meanwhile, is giving a fair imitation of his younger footballing self. Just over two hours since he left the car park, and after the steep, almost comically difficult final stretch, St Patrick's oratory on the summit reveals itself.
"St Patrick, he spent 40 days and 40 nights up here," says one woman as she surveys her Spartan surrounds. "There's not much of a set-up, is there?" Not much by way of facilities, no, but for anyone from Dublin, there's the odd assuring reminder of home: a cup of tea and a Twix is yours for €6.
On a small hill, a German film crew has trained its lens on the long line of penitents stretching from the oratory, where between 20 and 30 priests are on duty to hear what looks like a year's worth of Confession.
Heiko and his colleague are rapt. "What I like most, and you should write this very much, is the friendly people here. They laugh, they wave, everybody helps each other; it's great."
At the summit, the Archbishop of Tuam, Dr Michael Neary, devotes his homily to Ireland's immigrants, fitting on a day when the pilgrims traced the footsteps of one of our original - albeit by now reasonably assimilated - blow-ins.