My sketch hasn't quite caught the sharp contrast between light and shade on my shack. When I sat down the bright sun made the shadows - the left-hand side - almost black. Then the sun moved round and the sky clouded over. The shadows softened and shifted. So it's a mix of observation, recall - and invention. As usual.
As I sketched I was looking out for signs of the story of the shack. Once it stood in the corner of our garden. Then we took it to pieces and reassembled it on the allotment. We bodged the roof with corrugated felt screwed to an old pallet.
Unsurprisingly, the first gales ripped the roof open, and we were only just in time to rope it down and weight the roof with planks and bricks.
It's survived like this for over a year, looking like a badly tied up wooden parcel. Random but lovable.