They used to behead men like Tony Blair

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.

The conspirators, including Faliero, were arrested, tried and sentenced within 48 hours. In addition to the penalty for treason customary in the less politically correct 14th Century, the Republic saw fit to confiscate all of Faliero's considerable wealth, except for a small legacy of 2,000 ducats to his widow.
 
Fast forward 650 years to a United Kingdom trying to hold a political leader to account for deciding apparently by himself to prosecute a probably illegal war.

Along the way this leader concluded what amounted to a secret treaty with a foreign power to allow them unrestricted use of our armed forces - without the authority of either Cabinet or Parliament - but because, in his judgment, it was a good idea.
 
Where are the Signori di Notte when we need them?  Instead we have the Iraq Inquiry - a group of establishment worthies who give 'soft cop' interrogations a bad name, backed by terms of reference so flaccid that it seeks only to 'learn lessons' not to 'apportion blame'.  

It has no power even to order the publication of key documents, such as Tony Blair's letters to President Bush, let alone recommend prosecutions. Even if Sir Roderick Lyne, the only member of the panel with any forensic skill, manages to drive a stake through Blair's multiple evasions today, it won't amount to a hill of beans.  

Blair will leave the Queen Elizabeth Conference Centre at the end of the session, rejoin a security detail that would be over the top even in a banana republic, and be Range-Rovered off into the sunset to spend more time on his perma-tan and his millions.  

And unless the current government is prepared to take things further, there is nothing anyone can do. Cameron and Clegg won't, of course, act against a fellow member of a political class more closed even than Venice's 14th Century elite.  

But perhaps tonight, as David Cameron climbs the stairs at Number 10 past the photographs of his predecessors - our modern version of the frieze of the Doges - he will pause in front of the photograph of Tony Blair and contemplate the reckless damage he caused our country.  

We can't expect a black veil over the photograph. But what about a small Post-It note, even if it just obscures Tony's self-satisfied grin?
 
For the rest of us - if you are anywhere near Manchester Square today, you might pop into the Wallace Collection and draw comfort from Delacroix's great painting of ex-Doge Faliero learning his lesson. ·