Surferkris was correct. It has nails. I didn't seem to be getting anywhere with a hammer and hole punch so just cut 12cm off the 10mm middle tube, as recommend by phone a friend
Select to expand quotethedoor said..
Maybe. Is nailing battens a thing?
Yes, when the dimensions do not give room for a ferrule, then the parts are sometimes simply slipped directly into each other and held in place by one or two nails. This really weakens the tube batten though and it is not a good solution...
Sailworks sells the batten ferrules for a buck!, could assemble it with one if it fits your batten rod and tube (says what diameters it works with it), just make sure the overall length is the same.
www.sailworks.com/the-gear/batten-ferrule.html
It is a pity to cut the original tube batten, this can change the bending curve of the batten, but it might not be very critical as it is in a rather stiff portion of the batten.
What was the problem with removing the nails?
The ones I have seen did have a small head on them and you do need to drive it in the correct (reverse) direction in order to get them out.
Select to expand quoteSurferKris said..
It is a pity to cut the original tube batten, this can change the bending curve of the batten, but it might not be very critical as it is in a rather stiff portion of the batten.
What was the problem with removing the nails?
The ones I have seen did have a small head on them and you do need to drive it in the correct (reverse) direction in order to get them out.
partly I was worried that all the banging I did when I didn't realize there were nails in there impacted the structure of the 10mm section. And I was worried that the banging trying to remove the nail wasn't that healthy either. But mostly I was losing patience and for me this means using more force than is healthy for man made objects.
Also my sailing isn't at a level where I think I would notice any decline in bend curve 
Select to expand quoteSurferKris said..thedoor said..
Maybe. Is nailing battens a thing?
Yes, when the dimensions do not give room for a ferrule, then the parts are sometimes simply slipped directly into each other and held in place by one or two nails. This really weakens the tube batten though and it is not a good solution...
I fixed a batten for a friend, and what seem to work well for the joint, instead of putting in nails (!), is to wrap some fiberglass around it. I just cut a 5 cm patch out of 4oz/yard fiberglass (135 grams/meter?) and wrapped it around. Result is very thin and seemingly strong.
When all you have is a hammer saw, every problem looks like a batten that's too long. Or something like that. I think Albert Einstein said that once. I saw that on the internet somewhere.
Glad you have it sorted. 
Select to expand quotePaducah said..
When all you have is a hammer saw, every problem looks like a batten that's too long. Or something like that. I think Albert Einstein said that once. I saw that on the internet somewhere.
I think you saw that in the bible , but I believe Gandhi said it first .
