No matter how much you've heard or read about "the wall", there's no experience quite like hitting it for the first time. It's when the marathon turns from prologue into monologue, a sort of metamorphosis, that things start to get interesting.

Somewhere around the 18-mile mark in yesterday's Dublin marathon the legs turned numb. The feet were hitting the road like stone and the head was saying crazy things too horrible to repeat. This was it, the wall.

The wall has been the graveyard of many a great marathon runner. But when you're running 26 miles-plus for the first time - like myself - ignorance can be a saviour. You think about breaking through and recharging towards the finish.

Though the recharge never came, at least the finish did. Two hours, 31 minutes and nine seconds after leaving the city quays, the hard Smithfield pavement never felt softer. By then, the Africans were already in their tracksuits (they filled nine of the top 11 places). But my target was simply to finish. I am not a Kenyan, I wasn't born in the mountains, and I didn't run to school.

Tommy Maher used his experienced head to overtake me in the last half-mile, and become the fourth Irishman home. That left me the fifth Irish runner, and 23rd overall. Satisfied, considering those last four miles were undoubtedly the slowest four miles of my life. But then that's the marathon. It's not the distance that kills but the pace. If you've done any sort of decent training (and I had five decent months behind me) then those early miles will always be a breeze. And up to 18 miles, for me anyway, it was actually fun.

Just to run through Ballsbridge and Donnybrook without worrying about the traffic was worth the entry price alone. This was the leafy part of the course, the time to smile at the kerb-side supporters. Running alongside the smooth-footed John Griffin helped make this the easy part. Suddenly we were passing Stephen's Green, and the greatest congregation of crowds so far. A turn onto Clanbrassil Street and then it was halfway. The watch read one hour, 10 minutes. Bang on course for a 2:20 finish. But it's a long haul form here into Kimmage, and that right calf muscle doesn't feel so healthy now.

There was still a relaxed group of six. Griffin was pressing the pace, with Pauric McKinney and Gary Crossan the other Irish. Plus two foreign entries, and me. Next came a long stretch down Templeville Road. Strange how the wind now felt so much stronger. Too strong for comfort, and for the first time the stride becomes laboured. Down Whitehall Road I kissed goodbye to those brief thoughts about being the first Irish finisher.

Of course I passed the 18-mile mark but I don't remember it. There was now a steel bar running down my right hamstring and despite my best efforts the group of five were pulling away. At last another water station. Drinking on the run is an art in itself but I didn't care where the water went as long as it touched some part of my body. The next five miles would be a blur, broken only by some enthusiastic American voices. "Looking good!"

Chapelizod was just the spur I needed and even though Conyngham Road was agony every step of the way, the power of positive thinking is truly amazing. It was about 400 yards from the turn into Smithfield when Maher came past me, and I tried to go with him for all of about one second.

The second half of the race had taken me one hour 20 minutes. One thing to try and right the next time. After this though, there's simply one less thing to do in life.