Hi there, please can someone give me some advice. I have a 2005 RRS 4.2 V8 supercharged. Some times when I go to start it, it doesn't always turn over. I have to turn the ignition off and on, I can be sat there for half an hour before it will eventually start. I Don't think it's the battery because when it finally fires up it doesn't seem to struggle. It just starts as normal. Thank you in advance for your advise.

Manual says:

Symptoms:
The engine does
not crank (starter
motor does not
turn):

Possible causes:
Gear selector not in P or N
position (vehicles with
automatic transmission)
Battery
Starter relay
Invalid key code received by
central junction box (CJB)
Harness/Connectors
Starter motor
Ignition switch
Generator
Transmission control module
(TCM)
Engine control module (ECM)
Engine seized

Actions:
Make sure the gear selector is in the P or N position and correctly
adjusted. Check the battery condition and state of charge. Check for
DTCs indicating an immobilizer fault. Check the starter motor relay,
ignition switch and generator circuits. Refer to the electrical guides.
Check for TCM and ECM DTCs. Check that the engine turns freely.

You can probably ignore the 'engine seized' and not in 'P'

Also check the battery connections are tight and not corroded. 2008 MY Java Black TDV8 HSE

I have a similar problem, car starts up straight away within seconds as normal most of the time, but sometimes turns over longer then does finally starts up  RRS SUPERCHARGED, 22 INCH ALLOYS, JAVA BLACK, FULLY COLOUR CODED
EVERY POSSIBLE SOFTWARE UPDATE INCLUDING - BLUTOOTH UPDATE, SATNAV ON THE MOVE, CLOCK ON DASH, 3 CLICK FLASH, GEARBOX RESET, COMPRESSOR UPDATE AND SUSPENSION LOWERED,
BLACK CODE RE-MAPPED, AUTOBIOGRAPHY'D, NEW EXIDE BATTERY, NEW DENSO ALTERNATOR

Having the same issue that progressively worsens as the cold hits DC. I have changed the battery out and had a new Trans ECU a few weeks ago. I just ordered a replacement starter, but I feel that there may be an issue with the Shift interlock signal. I have tried shifting the transmission and jostling the shift lever during the key turn and I have found that the engine will start. This leads me to think there is an issue with the interlock. On the L322 the transmission had an external connection that was mechanical with a switch array. If this was out of alignment then the engine would not start as the switch was telling the ECU that the transmission was in gear. I know the ZF 6 Speed transmission on the L320 is a totally different animal. I am just hoping that this is the right area that I am looking. Does the Transmission selector in the cabin have the switch sensors within the lever assembly or is it yet again a mechanical connection that relays the lever position to the transmission? I believe there are Hall Effect Switches in the Transmission for the selector. Any thoughts guys!

Well having hunted around and not really fining anything of use on here or other Rover forums I found this very informative video.

Its not Range Rover Specific but it does indicate the issue of a Denso Starter and the Click