Councils have been of fundamental importance to the historical development of the Catholic Church. From the First Council of Nicaea in 325 CE to the reforming Second Vatican Council of 1962-5, the conciliar movement has more often than not represented the interests and prerogatives of the mass of the faithful: frequently - especially from medieval times - as a bulwark against the untrammelled supremacy of the Pope. Norman Tanner is arguably the outstanding...