The Annals of Cheskovscha

Marriage by proxy was not uncommon in England during World War I. Couples separated by great distances and for long periods of time found comfort in this real if not physical sacrament. It did, however, lead to some unlikely unions.
Among the Royals it was different. Victoria's numerous progeny were already checkerboarded by marriage across the length and breadth of Europe that all might continue to enjoy the privileges they were accustomed to. And their marriages for political or hereditary reasons had already produced many most unlikely couples such as a nice English girl wed to a cretin with a drool and vice versa.
Also the dislocation of people and populations resulting from the war left the status of most royal families uncertain as to who were still alive and if they were still enjoying the royal life style.
In an attempt to reestablish the age-old royal lines and royal prerogatives, proxy marriages were strongly encouraged by the Court. So it was that an English Viscount on a Grand Tour and caught behind enemy lines when the war began, simply assumed his other honorary position inherited from his grandfather, that of Colonel of the Second Regiment of the Swedish Christian Grenadiers and became a neutral and safe from internment.
He, and a Duchess by birth, also a Countess by marriage and a "Lady" in England were united at long distance in the bonds, or perhaps the bondage, of matrimony to protect her under his neutrality.
When they fictionally meet in a fictional Duchy on the Rhine a delicate situation results. It did not however interfere with their discovery and purloining of a German decoding machine for their country's Secret Service.
And a happy marriage.