Responding Seren Nos; so if you like this is an event as authorised by 100 Marathon Club, and abides to their rules, as well as Trail Running Association's where: "There is no requirement for trail races to be measured by qualified EA graded measurers." as stated by them,
and "distance can be whatever the event advertises itself to measure". And because it happens to be quite similar to marathon distance - but wasn't "officially measured" - it's advertised as approx 43km / 26.7miles.
I put "road" in the desscription to give the idea of running surface, otherwise this is considered as a trail marathon as guided by TRA.
I'm not going to re-write organisations' constitutions as I can see no reason why such evnt couldn't be advertised; I've had many entrants saying "looks a great way to spend NY's night, should see you there" after seeing it on RW and emailing me for info. Some people don't need any nfo at all seeing marathons on such date. People are different, runners are different and have different preferences of what kind of events to enter. If sb doesn't like sth, nobody tells them to take part. Why whould other people miss out on an event they like only because others don't think they should be advertised on RW.
Hopefully it has been clarified what kind of event it is and so people who are happy to do it will do, and people who don't like it att all simply will not.
With the insurance, I'll say that the event isn't covered - it's an "all to charity" event; there is no established organisation that makes profits from entries or otherwise and is thus able to put out big costy city marathons (we all know how expensive it is every year to put the Liverpool HM on and enries are higher than many "fancy" marathons). I can't afford to pay for the insurance from my own pocket, neither would I ever want to charge charities for it. But there will be First Aiders, maybe not a huge ambulance but First Aid trained and qualified volunteers. The route is extremely simple, always close to the start, and it's easy to retire from the event should somebody need to.
This said, althought back to back marathons appeal more to more experienced marathon runners, I wouldn't say it's meant to be limited to "hardcore runners" - I cannot see the reason why someone couldn't successfully finish their very first marathon here, on condition they feel 100% ready for attempting a marathon. If you're physically ready - it does require some training - and take care of nutrition well then why not? I've paced some people to their first marathon in 37 degrees and no water provided, despite the organisers' having claimed to do so beforehand. Also there should be a pace maker for 4:00 and one taking the slow group, 5:30 or 6:00.