Leucojum vernum aka Spring Snowflake. Could be in the form Gravetye Giant which is the one normally sold.

thank you Owdboggy

yes I also think it is Gravetye Giant. I love this bulbs. I have a good clump that flowers without fail every year.

It's named after Gravetye Manor, just down the road from me - a beautiful country house hotel with fabulous gardens. Wish we could afford dinner there.

It was originally found at Ingwersen's Nursery at Gravetye, many years ago. Sadly the nursery is no longer there as the last Ingwersen (Paul)died recently.

I used to walk my dog around Gravetye and walked past Ingwersens many times. It's a lovely part of the countryside. I remember when he retired and stopped exhibiting at Chelsea but didn't know he'd died. Lovely plants.