There was only about a mile left when the tech failure happened. The pace was slowing and the Brandenburg Gate was in sight when the final water station popped up on the right.
A desperado in front of me saw the outstretched plastic cups and veered drunkenly in front of me to grab one. He accidentally bashed my arm but I thought nothing of it as I grabbed a cup of my own for the final push.
But when I looked at my Fitbit, the impact had stopped the GPS timer and cut to the end-of-run summary screen. It had stuck on 25.2 miles - exactly one mile short of marathon distance with no way of restarting it. My first marathon would go unrecorded by Fitbit and Strava.
Maybe it was the fatigue or the adrenaline of the moment but it seemed really important at the time. I wasted valuable energy by cussing under my breath and wondered what to do for the best.
It had all gone so well until then. That September Sunday morning in Berlin was beautiful - sunny but chilly enough for me to wear a disposable M&S pullover and bright enough to need the Sunwise shades while I waited with 40,000 nervy others on the Straße des 17. Juni.
Deborah and I had made the 20-minute S-train journey from the Zoologischer Garten station near our Wyndham Excelisor hotel and walked with the giddy crowds from the Hauptbahnhof to the starting zone. I was smothered in vaseline in all the right places and feeling as slippery as a German eel. I'd breakfasted on a banana and a train station croissant plus a Morning Berry protein bar and an SIS Hydro sport drink.
My Batman-style utility belt was loaded with two mini bottles of SIS Go Electrolyte plus a couple of gels. I had an extra gel in my left shorts pocket and a handful of chewy gel Shot Bloks from personal trainer Yasmine in my right. I was a walking nutritional time bomb.
I left Deborah at the German Chancellery after a good luck hug and headed into the secure start area for a forty-minute wait for my wave to set off. I stretched, relaxed, marvelled at the runners of all nationalities gathered for this run-of-a-lifetime. We walked up towards the starting arch in front of the Siegessaule victory column. I seemed to be surrounded by Danes. Hooded crows flew across the road that divided the Tiergarten park. A final dash to the side of the road to shamelessly depressurise and I was ready.
The first couple of miles were slow through the sheer volume of traffic. I dodged and weaved through the pack trying to find a rhythm and a route amid the pattering running shoes.
By mile three I was starting to hit my race pace - around 8'34 per mile. I felt great. The streets were lined with cheering crowds, bands popped up every so often - a jazz quartet here, a steel band there, an oompah band on the right, a rock band on the roundabout on the left. It was exhilarating, thrilling and joyful.
And that was it. The miles rolled by with high-fiving kids and clapping pensioners lining the streets. I got halfway round and was delighted to hear a cheer from Deborah. There was plenty left in the tank and the legs were feeling good. The 60-minute Thursday night massage by Richard was paying off.
We raced through the utilitarian apartment blocks of old East Berlin and emerged into the leafy shopping boulevards of the old west. I felt as cheerful as a chaffinch - head up, smiling, hoping I wouldn't hit the dreaded wall. But there's not much of that left in the city anyway these days.
By 20 miles the outside of both knees knew they were in a race and my calf muscles were grumbling slightly but it was nothing serious. At 38km Deborah popped up again on the roadside to give another kickass cheer.
By 24 miles the calfs were complaining a bit louder and my pace slowed to 9'20 per mile. By now all the gels were gone, the bottles were empty and I was down to my last chew. I'd never run out of nutrition on my training runs but with less than a couple of miles to go I was out of fuel. I was heading into the unknown.
But the water station jostle and a glug of cold water were enough to provide that final psychological boost to press on for the finish line. I faffed about with the Fitbit and re-fired up the GPS for the last mile.
It was a fabulous feeling, running along the Unter den Linden towards the Brandenburg Gate with crowds cheering on either side, the finish arch ahead, the feet thumping on to the timing mat, stopping the bloody watch and slowing to a walk for the first time for nearly four hours.
The water kerfuffle meant I didn't have a proper unofficial time. I knew it must be under four hours and by adding together the long run and the short run a time of around 3hr 53mins looked probable. I wrapped myself in a yellow plastic binliner and feasted on a banana and a bottle of water.
I grabbed a medal and queued for a complimentary pint of Erdinger alcohol-free beer - not as bad as it sounds - than headed out to meet Deborah. I stretched out in the sunshine waiting for an official time.
I searched for my name in the iPhone app and there it was: I'd finished my first marathon in 3:51:30. I was pleased. I was hoping for under four hours and I'd done it fairly comfortably. Not only that, I felt great. The calves were already feeling better and after a bottle of SIS protein shake we walked to the finish line village to a buy a finishers' t-shirt, a bratwurst and a pint of real beer.
It was delicious. Ich bin ein Berlin Marathon runner.
