| Most likely the cable has bust, easy to check, just unscrew the cable at either end and twist one end. If the other end turns it's OK, well that's if both ends are crimped from the round into a squarish section, but my bet is that the cable will be broken about an inch or so from the speedo drive end and all you'll see is some twisted wires sticking out of the speedo drive. | 
Jools
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