In 1838 the situation was slightly the same as in 1831. Muhammad Ali of Egypt was not happy about lack of his control and power in Syria, he resumed military actions. The Ottoman army lost to Egyptians at the Battle of Nezib on June 24, 1839. The Ottoman Empire was saved by Great Britain, Austria, Prussia and Russia by signing a convention in London in July 15, 1840 to grant Muhammad Ali and his descendants the right to inherit power in Egypt in exchange for removal of Egyptian military forces from Syria and Lebanon. Moreover, Muhammad Ali had to admit a formal dependence from the Ottoman sultan. After Muhammad Ali refused to obey the requirements of the London convention, the allied Anglo-Austrian fleet blocked the Delta, bombarded Beirut and captured Acre. Muhammad Ali accepted the conditions of the London convention in 1840.
Who helped save the Ottomans by signing a convention in London? 
Great Britain, Austria, Prussia and Russia