It was 4C when I set out this morning, and I was worried that I would need another layer in addition to the undershirt and winter jersey I was wearing. I needn’t have worried — I was working up a sweat within a couple of kilometers.

After getting a bit turned around at the Imperial Palace, I was soon waiting for José at Nihonbashi. We didn’t have any firm goal in mind — I’d said, “Let’s just ride up Arakawa until we’re tired,” and he’d agreed.

There was a slight headwind when we reached the river, and we didn’t press hard. We soon came to a checkpoint where the police were assisting Girl Scouts in handing out safety brochures and tchotchkes to cyclists. I gamely accepted the pouch, only to have to stop to stow it in my bag so I could continue riding.

We went along upstream, stopping every 10km or so for a brief rest. Just before 11 we stopped to eat a couple of Nana’s world famous onigiri. I’d covered 40km by this time, and I vowed to reach 50 before we turned around. José was feeling the effects of multiple hours spent at the gym yesterday, and a lingering back injury (for which cycling is not a recommending remedy).

As luck would have it, the GPS chimed the 50km mark the moment I drew abreast of the Asaka Weir, and we paused to rest our hands and backsides before turning for home. I remember commenting to José that it was the Arakawa, and we could count on the wind being changeable if nothing else on our return journey.

We continued downstream, still stopping every 10km or so to rest. With about 10km to go before we left the river course, we stopped to have the last of the onigiri. We were glad to discover when we resumed our ride downstream that the gauntlet of Girl Scouts had disappeared.

Our final rest stop was a convenience store just a kilometer or two after we left the cycling course, where José treated me to a giant Kit Kat and I washed it down with a bottled latte. The skies had darkened considerably although it was just after 1 p.m., and I turned on my lights before we continued in city traffic.

We parted ways at Nihonbashi, where we’d met five hours previously, after a celebratory selfie. I continued on alone towards the Imperial Palace and around counter-clockwise until I reached Kudanzaka and paused for a last break at Tayasumon and Chidorigafuchi. After that it was simply a matter of plugging on along Shinjuku Avenue in Sunday afternoon traffic.

I rolled into the tower courtyard a bit after 3 p.m. and stopped the Garmie only to discover I was still 170m short of 100km. I resumed the ride and just did a lap down the path and back up the road to bring me once again to the tower entrance, and the Garmie beeped to let me know I’d completed 100km. I shut it off and garaged the bike, then headed upstairs to start the bath and enjoy a cold beer.