@johnjohnston It looks quite a bit like the evening primrose native to North America, which is unrelated to the Scottish Primrose (and looks nothing like it).
@johnjohnston Wikipedia mentions it was introduced to Europe in the 17th century. There's a map showing distribution here:
www.nonnativespecies.org/factsheet...
As the name implies, it blossoms at dusk in Utah where I've encountered it most frequently. But the blossoms last through the night and into the next day for a while.
@johnjohnston @oroboros ive only seen yellow evening primrose. I was going to say mallow, but the flower structure does suggest a Primula species. Could be an Oeneothera, but I can’t get a good look at the stigma.
@oroboros @jeremycherfas Thanks, I don't think Oenothera, they seem to North American, I found this quite far from cultivation so don't think it was an introduce or escapee. After a few twitter suggestions I now think it might be Wood Sorrel, quite a few miles away from the nearest woodland, and a bit higher than expected.
@johnjohnston yes, could be. I only have Oxalis tuberosa to hand and the flower structure is very similar. The leaf would clinch it.