It's a bit too early for wild garlic/ramsons, which usually flowers
from April to May. I strongly suspect the plant in question is Allium
triquetrum (Three-cornered Leek) which has become widely naturalised
in the south and is gradually extending north. It is very common
around here forming large clumps in uncultivated ground. It is
invasive and probably not recommended for inclusion in small gardens
unless rigorously controlled. The bulbs can be used as a substitute
for shallots (albeit very small ones), the leaves are quite pleasant
if chopped and added to salads and the edible flowers can be included
for a bit of visual interest as well.