Leaf appears channelled, like a stick of celery towards base. Large nuts! 4-5 by 2.5-3mm. Juncus tenuis?
EDIT 05/04/2018
'Leaves reduced, long culm, no obvious leafy involucral bracts' - Cam Kilgour
'A %^&$ to get out of the ground, nearly gave maself another hernia' - Andrew Marshall