Perhaps the most famous blue poppy of them all - it has for nlong been known as  GS600 (wrongly! - since like all the collections of Ludlow and Sherriff it should be L and S 600). The seed of this was collected by Ludlow and Sherriff in 1934 on the Nyuksang La in Bhutan. It was their 600 th collection that year. The first -  L and S 1 - was Primula gracilipes. They returned to collect seed later and is probably their most famous collection from all their trips both before and after the second world war. It does not set seed anymore but recent visitors to this area report very similar plants there to this day. They were fortunate to get seed since when they 

returned in the autumn to collect it the whole area had been trampled by yaks. All this is written up in 'A Quest of Flowers' by Dr Harold Fletcher of the R.B.G. Edinburgh (1975). I might add that even Dr. Fletcher called it GS 600!