[3] Reflecting the confused nature of Jacobite politics at the time, Sempill worked alongside, and sometimes against, Daniel O'Brien and George Kelly who had also been commissioned to represent Stuart interests in France.
[1] After the death of Cardinal Fleury, Sempill carried a message to Louis XV from several prominent from English Tories requesting support for a restoration of the Stuart line.
The French foreign minister, Jean-Jacques Amelot de Chaillou, replied that considerable proof of English support for Jacobitism would be required before France could act.
Sempill conveyed inflated and inaccurate confidence in the strength of the cause and a Franco-Jacobite invasion of Britain was planned towards the end of 1743.
The planned French expedition was, however, abandoned in the summer of 1744, by which time Prince Charles had lost trust in Sempill and publicly mocked him as "Lord Simple".