Smelly trumpet plant

can any one out there identifi a plant my mum has grown for years in her garden. It comes up every year with a large trumpet like flower which produces a terrible smell and attracts all the flies. It has now spread through out her garden. The flowers themselves can grow to about 2 foot and has large leaves. Don't get me wrong it is a very attractive looking plant, it has now finished growing and has vanished until next year hence not having a picture to show.