I was thinking about what defines a good walk.
I've done a few in my time - Le Puy to Santiago, the Pennine Way, Offa's Dyke - but there are just a few memorable days. Days that I look back on with a real feeling of contentment. And I mean the entire day, not just one episode or one sight.
So, what do they have in common?
Number one; a sense of shape.
From Pitigliano to Sovana is a marvellous walk. You ascend from Pitigliano on an ancient Etruscan via cava, a road carved deeply into the tufa cliffs. It's dank, shady, and the road is full of last year's fallen leaves.
Then you come to the plateau; a high, wide expanse of grass and meadow flowers. You can still see cart ruts graven in the limestone.
And then another via cava takes you into Sovana, a charming small town with Etruscan relics and a Romanesque cathedral. Then you can walk back, the wonderful shape of the walk from one valley to the other, in time for a dinner of wild boar dumplings and a bottle of the sharp white wine of Pitigliano.
That's what I mean by shape. Walking a ridge, or walking a valley, or a perfect circle.
Another perfect day: Saint Jean Pied de Port to Roncesvalles. The same shape; up and up and up, till you almost give up, and then a wide open plateau and finally, the downward path. And you've passed the Pyrenees. You were in France, you're now in Spain. Put that together with winter snow and the silence of the peaks, and it's unforgettable.
Another one: the Pennine Way from Middleton in Teesdale to Dufton. You head out of Middleton and you're in the wilds almost at once. You scramble up a waterfall; across some boggy moorland; and then suddenly you're staring down a v-shaped gash in the rock to the sunlit plains of the Eden Valley, hundreds of feet below, and the horizon seems to extend to the edge of the world. And then down into Dufton. Again, the day has a shape to it; a slow ascent to sublimity, then down again to comfort and charm.
Another day very like that one on the coast to coast, over Nine Standards Rigg with its weird stone cairns and down, down, down to Kirkby Stephen, a descent that just keeps on going. You had no idea that you were that high.
There aren't actually that many perfect days on a long distance walk. More common are the days with one or two great moments. The day in Burgundy that I started out along a ridge on the lip of a quarry at about six in the morning, and saw the dew on the funnel spiders' webs lit up by the first rays of sun. Once in Spain when I was walking across the meseta and suddenly found a gorge in front of me, and a whole village laid out at my feet.
And we're grateful for those moments, too. After all, it's in the nature of walking that so much of it is just hard graft - and you do want to feel you're earned your pleasure.