Wild Madder is in the bedstraw family along with cleavers, woodruff, squinancywort and all the bedstraws. There are two species of Madder, Wild Madder (Sherardia arvensis) is the one you will find in the woods and then there is Field Madder, which will be in the open.
I can’t recall having seen Common Madder in East Anglia, now I am in Gloucestershire it is quite a common plant. Symonds Yat is a good place to see it, it grows all around the viewing point where you can see the Perigrine Falcons. (has the scientific name Rubia perigrina got anything to do with Perigrine falcons?) Anyway I doubt that many people looking out along the Wye valley from this vantage point are likely to notice this plant at their feet but it is there.
This is what Wikipedia has to say about its name. The genus name Rubia derives from the Latin ruber meaning “red”, as the roots of some species (mainly Rubia tinctorum) have been used since ancient times as a vegetable red dye. The specific epithet is the Latin adjective peregrinus, -a, -um meaning “foreign, alien, exotic, strange.”
As with all the plants in this group the leaves are quite distinctive, being arranged in whorls of 5 to 7 at the joins (nodes) along the stem. The mature leaves of Madder are quite robust and are shiny and have jagged edges. Several species in this group have leaves with rough or jagged edges, it helps them grow up and gain purchase between other species and in the case of Madder over rocks and scree.
The leaves of this species remain throughout the winter so it is an evergreen plant. Also the stems are square and have little spines on the edges to help them get a grip on whatever they are growing over. It will tolerate shade but not acid soils so it is a calcicole ie will only grow where the soil pH is above 7. You can see from this distribution map that I would not have come across it whilst living in Norfolk. It is very much restricted to the western and south western coasts.
The flowers are not that spectacular with just four little petals arranged in a cross and a creamy yellow colour. Sometimes if quite a few come into bloom at the same time then they can make a bit of a show. It is the fruits which are more spectacular , they are quite big and spherical and when ripe a dark blue almost black colour. Like a mini bunch of grapes.
Here are a few more photos showing the flowers, I have yet to get photos of the fruits.