Amanda's Blue (polyommatus amandus) is quite variable according to locality and altitude. Before 2008 I had only encountered it in ones or twos and only at a few localities, but this year I have seen it in about 6-8 places, maybe more (I haven’t analysed my records yet) and most have had dark borders of varying strength (e.g. 10978), but I did see one like yours Paul (11836) in the Alpes Maritimes at the end of June.

- polyommatus amandus_10978.JPG (51.26 KiB) Viewed 452 times

- polyommatus amandus_11836.JPG (99.08 KiB) Viewed 452 times
It is noticeably large and pale silvery blue in flight, quite easy to ID once you’ve seen a few. I guess the only blue it could be confused with is Damon Blue (agrodiaetus damon), although amandus is significantly larger.
Escher's Blue (polyommatus escheri) is also large in comparison to e.g. a Common Blue, but not quite as large as amandus I feel. It (the male) is a strong bright blue and the black margin is always strong and the hindwing margins always have a degree of chequering, sometimes heavy but sometimes it is quite light and other blues can have this, so it is not definitive. The escheri underside is beautifully subtle and I always try to photograph it if I can.
When I am back in the UK in October I plan to put a comparison grid with all male undersides together on one page. In the meantime, I have put up some highlights of 2008 so far on my web page. There’s a female underside there, too – a beautifully marked butterfly. Not hard to guess my favourite butterflies!