1. Each constitution survived an average of four years after the first one was written, when a coup abolished the absolute monarchy in 1932.

2. Authorities in Thailand have warned Facebook to take down content critical of the monarchy, or face legal action.

3. But the two main parties in parliament remain loyal to the monarchy, our correspondent says.

4. Belgium has a constitutional monarchy in which the king plays a largely ceremonial role.

5. The imperial house of Japan is the oldest continuous monarchy in the world.

6. Along with the national football team, the monarchy is often regarded as one of the few institutions that actually holds Belgium together.