This grows in our neighbour's garden. Neither she or I have the slightest idea what it is!
Fruits are borne singly on the tree (which is currently about 15 feet tall), are yellow to light orange in colour, pretty much 2cm spheres with no dimple at the bottom. They smell kind of citrusy when you open them and have a single seed inside shaped like that of a plum.
Any ideas? Will we be able to use them for something and not die?