D'Eon was a captain in the Dragoons and had served France in diplomatic postings firstly in Russia and later in England.
He had been awarded the Cross of Saint-Louis during the reign of Louis XV in recognition of his service in the Dragoons and his diplomatic work.
During his time in England he fell out of favour with two of the king's ministers (a dispute having started over the level of his expenses), leading to his replacement by another diplomat.
In an earlier case (also before Lord Mansfield) it was held, on the evidence provided by witnesses (including two doctors) to a jury that Monsieur D'Eon was female.
It was not until this case that the Court (Lord Mansfield) considered the public policy issues arising from this form of wager.