Go to Venice to see how a vigorous state, proud of its democratic system of government, dealt with a ruler who sought illegally to concentrate supreme decision-making power to himself alone. To be precise, go to the hall of the Maggior Consiglio in the Doge's Palace.

Drag your eyes away from Tintoretto's astonishing Paradise, which covers the end wall, and look up to your left at the frieze of portraits showing the first 76 Doges.

Where there should be a representation of Marino Faliero (Doge 1354-55) there is instead a painted black veil bearing the words: 'Hic est locus Marini Faletro decapitati pro criminibus' - 'This is the place of Marino Faliero, beheaded for his crimes'.

The whole device was designed as a powerful and permanent warning, not to Venice's people - they were not allowed in the chamber - but to Venice's ruling elite.

Faliero was a distinguished military leader, elected Doge when 75 years old, but with a solipsistic contempt for the petty laws, customs and state offices the Venetian Republic had evolved in its first 500 years to limit the power of its elected head of state.

He judged that Venice would be better ruled by him alone as Prince, maybe with the help of one or two chums. The plot was uncovered by the Council of Ten (roughly equivalent to the modern cabinet) who in alliance with Venice's magistrates and its chiefs of police (the evocatively named Signori di Notte) moved with extraordinary speed and confidence.