The separation of powers in the UK

The most fundamental guiding principle underlying the British constitution
is that of the ‘separation of powers’. Based on the theories of French
political thinker Baron de Montesquieu (1689–1755), the Trias Politica is a
notional model that splits the state into three branches:
• the ‘executive’ (the government);
• the ‘legislature’ (Parliament);
• the ‘judiciary’ (the courts).
The idea is that, to avoid arbitrary or dictatorial government, a constitutional
framework is needed that does not confer too many powers on a single
individual (or small group of individuals). In theory, if the executive is
wholly ‘separated’ from the legislature and, in turn, the judiciary, each can
act as a ‘check and balance’ on the other.
Montesquieu formulated his theory based on the workings of the UK system,
although Britain’s democracy arguably adheres far less strictly to this
model than many that have emerged since. In practice, numerous overlaps
have emerged down the centuries between the roles, powers, and even membership
of the key institutions that are meant to be preserving the separation
of powers, including that:
• constitutionally, the reigning monarch (as ‘head of state’) is titular
head of all three branches of the constitution;
• until 2007, when the post was reformed (see p. 78), the Lord Chancellor
was actually a member of all three institutions, as Speaker of the
House of Lords (legislature), ‘manager’ of the legal profession (judiciary),
and a minister in the Cabinet (executive);
• the prime minister and most other ministers are members of the government
(executive) and the Parliament (legislature);
• prior to the expected establishment of an independent Supreme Court
in October 2009, the Law Lords were still the UK’s highest court of appeal
(judiciary), as well as being members of the Lords (legislature).
Such constitutional overlaps are not confi ned to Britain. Many other parliamentary
democracies—particularly those directly modelled on that of
the UK, as in many Commonwealth countries—display a similar fusion of
powers in practice, rather than the ‘separation’ to which they aspire. Constitutional
historians are increasingly drawing a distinction in this regard
between countries that practice ‘presidential government’ and those characterized
by ‘parliamentary government’. In the former (which include the
USA, France, South Africa, and Australia), separation is felt to be both more
practised and practicable than in countries such as Britain, where the most
senior politician (the prime minister) is today drawn from among the ranks
of ordinary MPs and, as such, is elected to a constituency in the same way
as his or her peers.
In the UK, executive decisions are taken primarily by prime ministers and
their ministers, before being presented for approval to Parliament (where
most of them are also present, this time as voting MPs and peers like every
other). In the USA and other presidential states, in contrast, the most senior
elected politicians are known as presidents—who, in the absence of reigning
monarchs, are also heads of state. Crucially, unlike in Britain and other parliamentary
states, presidents are usually elected on different timetables to
their national parliaments. The separation of powers in the USA is far more
pronounced than it is in Britain because Congress (made up of the Senate and
the House of Representatives—the US equivalent of Britain’s Parliament) is
elected in large part on a different date, and in a different manner, to the president.
More crucially, the president (unlike the British prime minister) is not a
member of either House; so while he or she may present policies to Congress
for its approval, he or she does not preside over the ensuing debate and vote(s)
within the two chambers in the way that prime ministers do in the Commons.
Another feature of the separation of powers enjoyed by presidential states
is the fact that, historically, they tend to have developed a more provably independent
judicial system than in many parliamentary states. To this end,
the USA has a Supreme Court that is, in theory, entirely separate from the
political process. Notwithstanding controversies over the president’s ability
to nominate judges to replace those who retire (President Bush was castigated
in 2005 for choosing Harriet Miers, his former adviser and a longtime
conservative ally, who later withdrew her own candidacy), this system
is felt to be better than one in which judges straddle the notional divide
bet ween legislature and judiciary by serving in both a legal and legislative
capacity. To this end, in 2007, Jack Straw, as inaugural Secretary of State for
Justice (and de facto Lord Chancellor) announced that the Law Lords would
be effectively removed from Parliament in 2009, to sit in the new US-style
independent court, the creation of which was approved in the Constitutional
Reform Act 2005.
Further reforms were promised by Gordon Brown during his fi rst weeks
in Downing Street, as part of a ‘new constitutional settlement’ for the British
people. Among those mooted was a law to formalize the tradition (notably
bypassed by his predecessor over Iraq) that Parliament should always have
the fi nal say on whether Britain goes to war.