How many is too many on a CL?

they would have to carry third party liability

That is the insurance that I am asking about being invalidated by more than the legal 5 caravans, OP.  If it is not invalidated at 5, maybe it is at 10, or 100? There must be a limit or there would be big sites insuring themselves as a CL to get cheap insurance.

Oddly, I have never seen a CL displaying a Certificate of Public Liability Insurance, as many other types of business are required to do by law.  Could this be another part of the exemption?

Back in the day (pre 2001) when we had a CL we displayed our insurance certificate. I can't remember if we were told to; it just seemed the right thing to do.

How strange and what a coincidence

On the last CL we stayed at we were third on and the day after pitching went out for the day. On our return the owner approached us and told us that the van opposite had arrived unexpectedly,adamant that he had booked and set up accordingly. Neither of the couple owning the site could remember it but assumed someone had forgotten to put it in the books. Anyway they asked if we would mind a 6th.van on site for 2 nights over the weekend as someone was arriving that day. There was room and we said we didn't mind as the owners were upset at their fault in not recording the booking.

Anyway the following day the owner saw us again and said that the caravanner had received a phone call from a cl about 5 miles away wondering if he was going to honour his reservation. Sheepishly he packed up and moved on. So sometimes it happens. It really depends on whether it's a regular occurrence or a one off. Regular and I'd report it, one off then I wouldn't.

Well I can see from a customer service point of view why the  Cl owners did what they did but legally to remain within terms of his licence they  should have done the latter. Who would stand by the CL owner if god forbid there was some sort of incident ( don't know what) resulting in loss of life , injury etc and the site was in breach of regulations. 

In mitigation 'custom & practice' within the wider CL owners community could be cited. Everyone knows it goes on including C&MC, it continues unabated so it becomes custom & practice.

And that is ok until something goes wrong and everyone that supports the practice  will run for cover. 

Some of you won't want to know this, so forgive me, but the nearest equivalent sort of rural site in France is called an Aire Naturelle de Camping - 25 pitches allowed, provided one hectare is available - so 400 square metres per pitch. The rules have recently been modified to allow 30 pitches instead of 25, so a bit less space than that.

The numbers are irrelevant. Hardly anyone uses those small rural sites. British visitors going over there rarely seek them out. Most Caravanners want full fancy campsites, and most motorhomers  want cheap hardstanding Aires. 

Oddly, I have never seen a CL displaying a Certificate of Public Liability Insurance, as many other types of business are required to do by law.

Nav - Public Liability is not compulsory in the UK, merely advisable. Most insurers do not issue an actual certificate for this insurance, just a policy. What you normally see displayed is a Certificate of Employers Liability insurance. This is normally provided by the same company that insures the Public Liability and will often carry the same policy number so this may be causing some confusion. Only those insurances that are Compulsory have a certificate issued, hence your Motor Insurance Certificate, which ironically only proves that you have Public Liability insurance! Still following me?

For a sole trader who doesn't have Employees then they will receive a policy document. Sometimes the insurer will provide them with an official looking declaration so that they can provide it to prospective clients or people who employ them as a sub contractor just to prove that they have this insurance.

D2, it's not about support just mitigation. Example-if a boss attempts to discipline a worker for not using safety gear the worker could point out that none of their co-workers use it either(mitigation) plus it's been going on for years(custom & practice)

Who would stand by the CL owner if god forbid there was some sort of incident ( don't know what) resulting in loss of life , injury etc and the site was in breach of regulations.

The answer would be that the insurers would pick up the bill, subject to their Limit of Indemnity. There are many occasions when you hear about a company being found guilty of breaching H & S rules usually where an employee or a member of the public have been injured or killed. The insurers don't rely on this to get out of paying as their wording specifically sets out to cover the Legal Liability of the Policyholder and if they are liable in law then the insurers will have to cough up.

The fact that the CL owner broke the regulations would probably be of more interest to the H & S Executive and the law.