The Rover-Landers of BC

I am new to this forum so I hope this question has not been asked before.
I have a series 3 and am on my third speedo cable. Driving down the road and I hear a sound like a spring snapping and find the cable no longer works. I read somewhere that its to do with the speedo itself not releasing when in reverse and winding up the cable? Just wondered if that's true and how I fix the issue. Any help would be appreciated.

I’m certainly not the expert on this, but I very much doubt that the problem is your speedo. IIRC, I had a similar issue on my 2A (or possibly a different vehicle I used to have). It seemed to me that the speedo cable housing was slightly too short for the cable itself. This caused the cable to be bound up (tight) when tightening the housing nut to the speedo. What I did was install a washer (or 2?) between the speedo and the nut, essentially making the housing slightly longer. On the negative side, it gave less thread engagement, but that didn’t seem to be a problem. If this is also your issue, another way to solve it might be to grind/file the cable end a bit shorter.