Re-inserting a continuous roller blind chain

[hounslowluddite]

Hi

I've got a roller blind at our kitchen window. The mounting to the wall has come loose causing the blind chain to slip out.
The chain is one-piece with no joining link in it. I need to fix the chain back in place, but there is no visible way to dismantle the roller mechanism: the bit that moves the blind up and down.

The outer edge of the roller mechanism has a hexagonal hole in it that looks as if it is designed to take a large Allen key and unfortunately I don't have a key of the correct size to fit it. However I do have a large one that I can file down to fit if this is the correct way to go about dismantling it!

Inside the inner edge there is a slot that looks as if is designed to accommodate a screwdriver blade.

These two slots suggest to me that if I hold the mechanism one side with a screwdriver and the other with an Allen key there is an internal thread that can be unscrewed. Is this correct?

Videos on Youtube suggest there is a screw to undo or a clip to release to allow dismantling but this one does not have either of these release mechanisms.

I remember having the same problem over a decade ago with a blind and not finding a solution then. In the end I forced the chain in place by prising apart the outer edge of the mechanism in order to force the chain into place but I did some damage to it in the process. It wasn't easy and I'd like to find out how to take these apart the easy way, if there is one.
Thanks if you can point me in the right direction.

 

[hounslowluddite]

Don't bother replying to this query. I've just re-attacked the problem; clamping the roller mech in a vice. With a pair of long-nosed pliers I've found that this is a push fit, which was my original impression. I'd tried releasing it this way earlier, but without the vice in use I'd not been able to apply enough pressure to break it apart. Thanks for your time if you've looked in!