metallic clunking at drive shaft

that's best how to describe it ...

at worst it is real annoying, but it only shows itself every once in a while.

I had a look today at the drive train and this is what I found:
- rear flex joint looks new and has no cracks
- ditto to front
- bearing carrier has some play, but it's not loose and looks OK
- rubber boot covering splines in tact and splines are clean and lightly greased.
- no other drive shaft sounds (i.e. humming or the like)

when banging against the front section of the drive shaft I managed to recreate the annoying sound. It sounds like there is another tube inside the drive shaft and that by banging against it (by hand) I manage to get the two to 'clunk'.

Is there two sections of pipe in the front part of the drive shaft ? What would be loose inside the shaft ?

It must be of considerable length (about the same as that of the outer shaft) and affixed by flexible means to cause the symptoms I describe.

Does this sound like any known part of the drive shaft front half ?

As I said, it's rather annoying, very intermittent and looks like it will cause the shaft to be removed to get to the bottom of this ....

Any pointers into this will be appreciated !

oh, it's a Euro 200E 4 speed manual.

TIA
L