Which of the following countries does not have a single written Constitution compiled in one document?

Introduction / Context:
Most modern states have a written constitution, a single formal document that sets out the basic principles and structure of government. However, there are a few well known exceptions. General knowledge and polity questions often ask which country does not have a single written constitution, because this feature makes that system unique in comparative constitutional studies.

Given Data / Assumptions:
- The question asks about a country that does not have one single written constitutional document.
- The options include United Kingdom, Australia, United States of America, Bangladesh and Canada.
- We assume the question refers to the traditional understanding in comparative constitutional law, where unwritten or partly written constitutions are distinguished from codified ones.

Concept / Approach:
The key concept is that the United Kingdom is famous for having an unwritten or rather uncodified constitution. Its constitutional rules are spread across statutes, common law, conventions and other sources, rather than contained in a single binding document titled Constitution. In contrast, countries such as the United States, Australia, Bangladesh and Canada have written constitutional documents that serve as a central reference point.

Step-by-Step Solution:
Step 1: Recall that the United States has a formal written Constitution adopted in the eighteenth century, which rules it out as the answer. Step 2: Remember that Australia has a written Constitution that outlines the federal structure and powers. Step 3: Note that Bangladesh also has a written Constitution adopted after independence. Step 4: Recognise that Canada, while having some complexities due to British ties, nevertheless possesses written constitutional documents, including the Constitution Act. Step 5: Identify the United Kingdom as the country widely cited as having an uncodified constitution, which is not contained in a single written document.

Verification / Alternative check:
Standard polity and constitutional law textbooks clearly contrast the British system with codified constitutions elsewhere, describing the United Kingdom constitution as unwritten or uncodified. In contrast, they refer to the Constitution of the United States, the Australian Constitution, the Constitution of Bangladesh and the Canadian constitutional acts as written references. This comparative treatment confirms that the United Kingdom is the correct answer.

Why Other Options Are Wrong:
Australia: It has a formally written Constitution, making it a classic example of a codified federal constitution.
United States of America: The written Constitution is one of the oldest in the world and is central to that political system.
Bangladesh: It has a written constitutional document that sets out the framework of government and rights.
Canada: Although its constitutional history is complex, the core principles are codified in written acts such as the Constitution Act and Charter of Rights and Freedoms.

Common Pitfalls:
A frequent pitfall is confusing the idea of very old laws or multiple amendments with not having a written constitution. Another mistake is thinking that if parts of a constitution are inherited from another country, it might not be considered written. The defining feature for this question is whether there is a single codified document called the Constitution, which is absent in the case of the United Kingdom but present for the others.

Final Answer:
The country listed that does not have a single written Constitution compiled in one document is the United Kingdom.