I think easily misidentified zuzu.
Look at the leaves on this Lemon tree ..
http://www.moonvalleynurseries...
I think this is a type of citrus. The fruit shape is similar to Tangelo, a cross between grapefruit and tangerine.
http://www.moonvalleynurseries...
I can't find a decent shot of the leaves.
https://www.google.co.uk/searc...
