Malva sylvestris. This is one of seven different Mallows to be found in Britain and this one is also found in North America where it is called High Mallow. Pliny said of these plants: "whosoever shall take a spoonful of the juice of any of the mallows, shall that day be free from all diseases that may come to him." Would that were the case!
Country folk in both France and England have used fresh mallow leaves soaked in hot water as an effective poultice for "strains, sprains and wasp and bee stings". Indeed a bee-keeping builder of ours advised that Mallows (Marsh mallow in particular) were good for bee-stings and to always have some growing in the garden. In the past it was recommended that mallows, boiled and buttered, be used 'for the Breasts or paps of women: for it not only procureth great store of milk . . . but aswageth the hardness of them . . . also all other torments that come by the stoppings of the belly.' I would assume it was the heat from using these as a fomentation which brought relief, in combination with the healing powers of the mallow leaves. Mallow was also recommended for treating pleurisy and other chest complaints, as well as skin irritation. Mallow root was used to whiten teeth. The plant is rich in mucilage, and for this reason was used in ointments and cough medicines, as well as in enemas!
Of course, the Marsh Mallow was used in the manufacture of the sweetmeat of that name - there must have been many millions of plants compared with today, when it is a lot rarer.
You will find the Common Mallow along roadside verges and rough ground.