sunloving pink flowers

I checked as many sources as I could to try to provide a name for these beauties, but to no avail. They twist closed in the shade and at night, and open up to reveal a yellow centre in full sun. There are loads of patches along the walking paths in this area, and act as ground cover plants too.

Does anyone know what they are? They may not be native, as the early settlers in this area were rather careless with flowering plants, so now we have a charming village festooned with freesias and sweet peas. Pretty, but not really allowed these days.