In the final part of the saga, Catherine and Potemkin return to St Petersburg after the glorious Dnieper tour. It is not long before the Ottomans declare war, and Potemkin \u2013 older and growing more ill by the day \u2013 is forced back out to fight for Catherine and for Russia once again. But a seeming hesitancy on his part delays the invasion for several months, and the Empress begins to worry that the ageing commander has lost his nerve, giving his political opponents opportunity to strike. The personal tension and exertion of war take a toll on both the former lovers and as she begins to retreat from public life and slowly deteriorates, the Empress begins to consider the matter of ascension. Catherine the Great - Thursday at 9.00pm on Sky Atlantic.