As I don't really have a great need to visit the forum on a regular basis (I've not owned an LPG vehicle for well over a decade) I didn't realise until I attempted to login this evening.
Investigations have found that this was due to a DNS misconfiguration although the reason for that change is unclear as the domain owner had not had cause to make any changes. Correcting the configuration has restored access to the forum and investigations are ongoing to determine what actually happened.
What I can say is that this server was not compromised and no data breach has occured. With the DNS misconfigured the server was essentially sitting idle and users attempting to access the forum were being directed to a different server altogether.
Apologies for any inconvenience this may have caused - but sometimes technology goes wrong