The bent family of grasses are exceedingly common although usually only on acid soils. As a result the common bent (Agrostis capillaris) in particular is a species of heathland and the acid grassland that frequently occurs where the heathers, gorses and other typical heathland flora give way to a lawn expanse of dense bent grass. It prefers dry conditions. The florescence of common bent is usually brownish in colour and is very fine in structure making it appear quite glossy. Indeed, one of its other common names is brown top, it appears over whilst in fact it is still in full 'blossom'.
Common bent is used extensively for lawn grass and is commonly used on golf courses where, according to Wikipedia, it gives some of the best playing surfaces in the world. Obviously, in these conditions it is carefully managed and regularly cut so one never sees it at its best, an expansive sward of gently swaying flower heads. If left uncut it can grow to two feet tall but normally one would expect to see it about a foot or so high.
I find this very difficult to tell apart from its close relative creeping bent.