I was involved in an accident with another Diamond insured driver and Diamond assigned responsibility to the other driver. It took them over six months to sort out the claim and that was only after threats of possible legal action from myself.
I have spent hours on the phone trying to move things along and am always promised something will be done but it never is. When i call back i can never speak to the same person, and the call centre staff vary from polite but not much help to rude and arrogant (despite always being polite myself).
I was promised a courtesy car but this has never arrived, and when the work on my car was eventually done (by a garage miles from where i live) i was told that i would have to collect the car myself despite the TAX and MOT running out while the car has been waiting for repairs. I have now moved insurance companies and am paying slightly more than half what i was paying with Diamond. I strongly recomend you shop around if your thinking about using Diamond