Many thanks to Futility Closet for this clipping from The Times, 9 May 1854:

An accident, the consequences of which are expected to be fatal, took place at Cannes on Sunday last. A M. Despleschin, of Nice, had announced his intention of making an ascent in a balloon, and two gentlemen, M. Hardy, of Cannes, and M.A. de Sorr, a literary man from Paris, had made arrangements to accompany him. These two gentlemen had taken their seats in the car, M. Despleschin not having yet entered it, when some person in the crowd, anxious to see the balloon start, cried out ‘Let go.’ The man who held the ropes, thinking that the order had come from the aeronaut, obeyed, and the balloon rose rapidly into the clouds, and disappeared. M. Hardy and M. de Sorr are both entirely ignorant of the management of a balloon, and it is feared that they have been carried out to sea. Up to the 2d. no intelligence had been received of them.