St Vincent had to weigh keeping Napoleon in Toulon against allowing him to take a large army far from France. A force heading toward Britain would still face the squadron at Gibraltar and the British squadrons covering France and home waters. Letting the expedition sail would also remove Toulon's best and readiest ships, leaving a smaller fleet to blockade. Nelson could follow the expedition while St Vincent cut its route to supplies from Toulon. In this interpretation, removing Napoleon and the victorious Army of Italy also offered a chance that revolutionary France would collapse without them. The strategy depended on isolating the expedition after departure and controlling its reinforcement route.
Chapter · 30:36-42:33
The strategic case for letting Napoleon leave Toulon
Letting Napoleon leave Toulon could remove his army and the readiest ships while Nelson pursued and the blockade restricted resupply.