http://online.carmarthenshire.gov.uk/agendas/eng/LICC20100504/REP06.HTM

The following comments from John King:
A unique twist to the two-in-a-bar rule. Two musicians are OK. Three or more musicians and Carmarthenshire Council insist on door supervisors.

"Whenever regulated entertainment takes place with more than two performers door supervisors should be ...employed".

Of course the 'two-in-a-bar rule' is no longer in the legislation and the number of musicians is not a factor but the employees will pay no attention to these small technical points.