Ruskin’s is a presence which will not go away. Depending on your state of mind he is either the sublimely indispensable guru whose influence changed forever the way we look at paintings and buildings, or else a half-crazed old fusspot dogging our aesthetic footsteps with the relentless tenacity of the Ancient Mariner’s ‘frightful fiend’. His amazingly fecund inspiration casts its gleam – or its shadow, if you prefer – over everything from art history, architectural theory and travel writing to sociology, psychology and ethics. Nowhere do we feel his pervasive authority more powerfully than in Venice, the city with which he developed the most complex of all his emotional relationships.

As so often in a love affair pretending to any kind of depth or intensity, the connexion was seasoned almost from the outset with disappointment. What Venice wasn’t became just as important for Ruskin as what it had been or once aspired to be. An ecstatic initial visit