Silly little question!

Sorting out why my speedo doesn't work, and have found the inner cable shaft doesn't turn. I want to split the cable at this connection. The knurled bit turns, but doesn't seem to unscrew, and I have tried moderate force to pull the connector apart, but no movement.
So, the question is - do I pull really hard to separate the connection, or should it unscrew?

Not seen one like that before, normal to find one piece cable.

I've got the two piece, as shown here. It looks as though the cable should just pull out of the end with the knurled fitting, but I want to check before using my almost superhuman strength and busting it.

Tried to attach a PDF of the spares manual, but too big. Part numbers for the two sections are PRC3718 and PRC 3724