Return of a Transportee!!

[KPM]

Hi
This may be a bit of a silly question, but I have a relative who was transported to Van Diemans Land in 1837 for 7 years.  Everything I have read tells me it is highly unusual for a convict to return to England once he/she has been transported.   However, in 1851 this relative is there, large as life, in the census - back home again with his mother.  There is no doubt it is him and no doubt he was transported.
Is there anyway I can find out how and when he returned to England?

KPM