Yep, sounds like the issue alright. Definitely a cranking speed issue of some sort anyway, these engines are sensitive to it for some reason.Thats a test I should do as I have seen that before it is better with the new battery as the old one just started to die whilst trying to start it.
To be honest I might just remove it as the French Car forum tell me its this I would just like to be certain as being very tight I don't want to waste my money!
First one I have seen held on with Allen bolts?