I have never seen the plant elsewhere, but no doubt someone here will recognise the description and tell me that is is common.....................
I remember the same plant in my mother's garden going back many years and the clump only ever increasing in size very slowly indeed. Now in my own garden it will have only around 30 flower stems this year.
The leaves are lax and around 10-15mm wide and to 30cm long, and unremarkable except that they are completely evergreen. Although the clump of bulbs is probably no more than 15cm or so across, the rather untidy leaves make the clump look all of 60cm across. This evening the flowers, only just starting to open here in the Midlands, have a very faint scent.
I have often wondered about its identity and no description on the www comes particularly close.
I could post a photo' if that would help.