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Well I never, I saw it yesterday at Midhurst sand pit too...
How funny! I first found it at Heyshott in 2008 (and misidentified it as sanguinalis). I looked every year after that with no further success. After seeing sanguinalis in Somerset last year, I dug out my herbarium specimens and realised that they were different, so sent one off to Paul Harmes for confirmation. After seeing sanguinalis in Petworth (in profusion along a road) this year, I was prompted to look again at Heyshott and Hey Presto! It's there in quantity!
Is it obvious at Midhurst sandpit? I visit there quite regularly (nice Small Cudweed amongst the broken glass!!)
that's the place - with Centaurium pulchellum (and erythraea) and dwarfed land-locked Crassula helmsii. The plants were only about 2 cm though. Some very dwarf Plantago major there too.
Saw sanguinalis just south of Iping about 30 years ago, not seen it since!
Just added my picture, and one of the Plantago major susbp. intermedia
Lat/Lng: 50.95915, -0.72415
OS grid ref: SU897185