So Civil Procedure Rules have absolutely no bearing on this type of claim? Or put another way, their claim is not within a CPR?

Hi all First post, I've tried searching for the info I require, so apologies if it's already been posted elsewhere. I won't go into the case as it's pretty standard stuff as in other threads - got a letter claiming as RK I was libel, and I'm not, etc. I followed the template letters virtually to the letter and following my second letter asking them to provide evidence of driver and case history, they've sent me a letter saying I must provide the name and address of driver of the vehicle on the day in question otherwise this may constitute (key word 'may') a non-compliance of the pre-action protocols (they quote Paragraph 4.2 of the Pre-Action Protocol earlier in the letter). I know I should have just ignored it, but I'm actually enjoying myself!! My next and final letter will be as per the templates i.e. no evidence so cease & desist and thats the last they'll hear from me. However, I am intrigued as to what the "pre-action protocol" is, and hopefully posting this might help anyone else who gets this quoted in a letter. Any ideas?