The diplomatic case for a separate constitutional monarch

What practical advantages can a constitutional monarchy offer over combining head of state and head of government?

It can provide a separately funded, politically neutral head of state whose continuity and ceremonial role may carry diplomatic value.

The practical case offered for Britain's constitutional monarchy begins with a head of state who is separate from elected party government. Much of the institution's financing comes from the Duchies of Cornwall and Lancaster in this account, which changes the usual argument about public cost. Its longevity and ceremony can put visiting heads of state outside their normal political setting. Members of the royal family can also make visits as formally neutral representatives, provided they remain politically neutral. These features are presented as diplomatic advantages, while the exchange acknowledges that such an institution probably would not be invented from scratch today.