Quote from their website:-
The Chiltern Model Railway Association (CMRA) was founded by a small group of local model railway clubs (centred around Hertfordshire, England) in 1965 to facilitate the avoidance of clashes of exhibition dates, provide a means of communication between the clubs and encourage mutual support.
Its aims are best summarised in the key phrase "to encourage and promote the model railway hobby". Since that date the Association has gradually expanded. Now with approximately one hundred and forty Associate organisations, the Association covers a large portion of the UK.
The membership includes a number of national "scale/gauge", company and nationality interest groups. In all, the Association can be said to represent over nine thousand individual modellers.
The range of services offered to Associate organisations has expanded over the years and now includes exhibition insurance, portable appliance testing (PAT), loan of exhibition equipment, exhibition diary, layout register, guidelines for running exhibitions, modellers workshops and seminars. The Association also publishes an occasional electronic magazine CaMeRA which is distributed to member organisations. Membership is primarily open to any bona fide organisation with an interest in the hobby.
Since January 2016 membership is also open to individuals and members of the trade.