Range Rover Classic

Couple of issues with 1990 RR classic V8, doesn’t get used everyday so went to start it and flat battery, put a jump pack on it and it started but the speedo went all the way round to 130 and won’t return to Zero. Rev counter works ok as does fuel and temp.
Stop the car and it won’t start - completely dead no lights no solenoid click etc completely dead - starts with pack again.
About to try a different battery but the speedo still stuck round at 130 - never come across this before and looking for ideas

I should get a new battery in place before going any further

….. and give all the earthing points a good clean.