Confidence: I'm as sure as I can be.
Notes: Stamens 3 (Fig. 4). BSBI Plant Crib: The leaves have air-filled tubes (aerenchyma) with cross-walls or diaphragms at intervals dividing them into sections. The pattern of the diaphragms is characteristic and may readily be seen through the hyaline inner surface of the sheath just below the ligule (Fig. 2); aerenchyma width 0.3-0.5 mm, inter-diaphragm distance 3.0-8.2 mm. Male glumes obtuse, purplish-brown (Fig. 3).