The foreign policy of Castlereagh was really different from that of Canning. This is what ultimately led to their dueling it out between each other. They both had a different view on the way that their country should proceed. This resulted in the battle between them because they could not agree on whether to send troops to Portugal.
Yes, the foreign policies of Castlereagh were different from that of Canning, because the two thought that they were different enough to duel over. In fact, the duel was over a disagreement over whether troops would be sent to Portugal. This was a significant disagreement that resulted in the two dueling over the issue.
No, the foreign policy of Castlereagh was really different from that of Canning. When you get down to the brass tacks of the situation, foreign policy is all about gathering as many friends as you can using whatever is available at the moment. In each case, each man was acting pretty much the same way.
The foreign policy of Castlereagh and Canning were actually much more similar than most people realize. A lot of people like to say they treated foreign policy with different ideologies, but that really isn't the case. In fact, they may have thought differently, but they reached the same policies nonetheless.
As the British Empire's power waned in the early 1800s, both Castlereagh and Canning agreed that a military solution was the only way to defeat French Emperor Napoleon I. Both men were in charge of military matters at different times during the rise and fall of Napoleon. Despite their differences that led to their 1809 duel and Canning's wounding, both men were essentially the same.