The Battle of Hafrsfjord has traditionally been regarded as when western Norway was unified under a single monarch for the first time.

The two kingdoms, known as Denmark-Norway, operated in a personal union under a single monarch.

Between 1931 and 1983 nine other previous British colonies attained independence as kingdoms, all, including Canada, in a personal union relationship under a shared monarch.

I'd rather live under a hereditary monarch who tolerates those freedoms than an elected president who doesn't.

At the first meeting of Parliament under a new monarch there is no speech from the Throne.

Linking/co-ordinating the two parliaments fell to a government under a monarch wielding absolute power in theory but limited in practice.

Government: Federal parliamentary democracy under a constitutional monarch.

For decades, the English had lived under a monarch who refused to provide an heir, but James arrived with a family and a future line of succession.

In summary, then, the fourth element of the Constitution - parliamentary government under a constitutional monarch - may be seen to comprise different relationships and powers.

They did not unite under a monarch until King Saul in the 11th century.