Hennessy surveys the constitutional building site opened up for the whole of the UK by the Scottish referendum, offering personal impressions of the time when the 300-year-old Act of Union was called into question and when he, as the UK's foremost expert on our unwritten constitution, became an important voice in what may happen next.
It is 1868 and the Imperial Cabinet of Russia is proposing an international agreement to forbid the use of certain projectiles in time of war - the St Petersburg Declaration.
