It is a neophyte and broadleaf semi-evergreen shrub which is grown in gardens but can escape to the sides of fresh water such as lakes, rivers and canals. It has a long flowering season from May to November and is native to South Africa where it was used to inebriate boys in some sort of initiation ceremony.
The long tubular flowers resemble those of:
Red Tobacco (Nicotiana forgetiana),
Angel's-Trumpet (Datura ferox) but those flowers are white,
Cigar Plant (Cuphea micropetala) but although it has a long red tube that does not escape into the wild in the UK,
Californian Fuchsia (Zauschneria californica) which also has red flowers but they stick out sideways, Hedge Fuchsia (Fuchsia magellanica) which has red flowers which hang downwards but they also have much longer petals (and only four of them) and an extra purple skirt from which the red anthers are exserted. There are many others. However, none of these have square stems!
Uniquely identifiable characteristics
Distinguishing Feature : A 'figwort lookee-likee but one which has long, dangling, tubular flowers which are red.
No relation to : Powell's Cape Lily (Crinum powellii),
Cape Pigweed (Amaranthus capensis), Cape-Pondweed (Aponogeton distachyos),
Cape Cudweed (Gnaphalium undulatum),
Cape Tulip (Homeria collina),
Cape Marguerite (Osteospermum ecklonis),
Cape Wattle (Paraserianthes lophantha) nor to Cape Gooseberry (Physalis peruviana) [plants with similar names belonging to differing families].