At various times in the history of the CAP, member states have formed informal groupings to address particular issues, e.g., 'the Aachen Five' and the agri-monetary system. The G-21, in effect led by France, is a much larger grouping which constitutes a qualified majority in the Council.
It become the G-21 rather than the G-20 at a meeting in Vienna when Greece joined. This left only the four leading reform countries (UK, Denmark, Netherlands, Sweden) outside the grouping, plus Cyprus and Malta - countries that have small farm sectors and may not have thought it worth the time and effort.
It's evident that this grouping forced the Commission to climb down on the Milk Fund issue and allocate an extra €280m to dairy farmers. This decision was apparently taken by Commission President Barrosso rather than by farm commissioner Mariann Fischer Boel.
A real concern is that this grouping could constitute a basis for mobilisation against further reform of the CAP.