[Wikipedia]
Fusion of powers
https://en.wikipedia.org/wiki/Fusion_of_powers
Fusion of powers is a feature of some parliamentary forms of government, especially those following the Westminster system,
where the executive and legislative branches of government are intermingled.
It is contrasted with the European separation of powers found in presidential and semi-presidential forms of government
where the legislative and executive powers are in origin separated by popular vote.
Fusion of powers exists in many, if not a majority of, parliamentary democracies, and does so by design.
However, in all modern democratic polities the judicial branch of government is independent of the legislative and executive branches.
The system first arose as a result of political evolution in the United Kingdom over many centuries, as the powers of the monarch became constrained by Parliament.
The term fusion of powers itself is believed to have been coined by the British constitutional expert Walter Bagehot.

2 Advantages
One advantage of a fusion of powers, according to promoters, is that it is easier for the government to take action.
There exists virtually no way for there to be a deadlock in the manner that can sometimes occur where the legislature and executive are separated,[8]
but see the 1975 Australian constitutional crisis for a counter-example (regarding the dual executive nature of some parliamentary systems).