ABSTRACT
Given the strength of the iron cage of party discipline in the post-1945 era,
Rose professed in 1986 that the only evolution open to parliamentary party
groups (PPGs) was towards less unity.1 If anything, however, discipline in par-
liamentary parties has continued to grow in strength. In particular, the decline
in discipline during the 1970s in the UK House of Commons that appeared
to inspire Rose has not proved persistent. Even the US Congress allegedly
witnessed a return in force of parties in the 1980s.2
