This walk was undertaken over two May days. Weather was hot, almost cloud-free and wind-free. So the overnight bivvy at 700m on Foinavon is not going to be repeatable very often. But I was there and grasped the once-in-a-lifetime opportunity.
The route

The walk started at a small car park at Achfary. I didn't get going until 13:00, having travelled overnight on the sleeper train from London then driving a hire-car for 2+ hours after that.

The walk begins on a so-called "Argo" track. The old path was widened in recent years to take 8-wheeler Argo trucks, but work is now being done under the auspices of Natural Scotland to reduce the visual impact. The first two miles on the track helped to loosen the legs up after my long journey, but then I peeled off to take the indistinct path up Arkle. The photo below shows the hut at Lone on the walk-in.

Arkle has two tops. Mis-leadingly the OS map associates the name with the lower top. Given the heat, and the lack of anyone around, I had my first go at naturist walking for the section between the two tops. Such fun!

Descending from Arkle to the east was a bit of a slog, because of the bouldery terrain. The original plan had been to bivvy at 400m on Bealach an Easaine Uaine, the low-point between Arkle and Foinavon, but it was only 17:30 and there was five hours of daylight left. There could be time to complete Foinavon before bivvying.

So I headed up An t Sail Mor at the southern end of Foinavon, which offers the easiest access to the ridge. On reaching the first top at 770m, I realised that the weather meant a mountain-top bivvy was feasible. I started along the ridge but quite soon found the perfect grassy spot. It was still only 19:30 but there's no rush to complete today.

The photo below shows the evening sun at my bivvy spot on Foinavon.

The bivvy was a great success.The sun was up and warm by 05:30, so a quick breakfast and I was on my way by 06:00, textile-free of course. The terrain became very fractured and care was needed on the first bit of descent. I felt fit and was moving well, and completed the ridge before 08:00, but was glad that I'd bivvied first rather than attempting it whilst tired.

The descent from Ceann Garbh to the north-east was slow-going. Nothing technical, but more bouldery terrain, and it took a good two hours to reach the track in Strath Dionard - where I reluctantly (and unnecessarily it turned out) got dressed.

The track ends at Loch Dionard but a reasonable path continues along the western side of the loch, where it joins up with the Argo track back to Achfary. Now that was a slog in the heat...

But what a joy the walk was. Apart from a couple of distant figures I saw no-one. The naturist walking in such heat was comfortable, practical and liberating.