Palmerston weighed French influence in Egypt against Ottoman survival when choosing sides.

Evidence

This has prompted some historians to argue that Palmerston had not made up his mind yet as to which horse to back, as it were, the Sultan or Mehmed Ali. At this crucial time the question in Palmerston’s mind was: would British interests be harmed more if Mehmed Ali was opposed by Britain, which would cause him to be swayed even more towards France and therefore increase that country’s influence in Egypt, or if he were allowed to get away with his attack on the Sultan, thus jeopardizing the very existence of the Ottoman Empire? — Khaled Fahmy, All the Pasha_s Men_ Mehmed Ali, his…, 1570