The UK government link is pretty harsh about Mr. Fox
See the following link: http://www.fco.gov.uk/en/about-us/our-history/a-brief-history-fco/foreign-secretaries/fox
I quote from the opening paragraphs in the above link:
"Charles James Fox
Foreign Secretary between:
Mar-Jul 1782
Apr-Dec 1783
Feb-Sept 1806
Fox was a gambling addict, womaniser, debtor, and dandy who was forgiven his failings by many because of his defence of civil liberty and his overwhelming charisma. He was Britain's first Foreign Secretary. In fact, he was Secretary of State three times, in 1782, 1783 and 1806, but each time he used the position more successfully to fight for a constitutionally stronger Parliament than to achieve foreign policy aims.
In 1782, the Foreign Office was a new endeavour, and it was much smaller than it is today. When Fox took the post he had only 13 staff in London, one of whom was a 'Necessary Woman'—the housekeeper. The total number of consuls and diplomats abroad was not much bigger. The Office was created because the Northern and Southern Departments that had dealt with home affairs, colonies, and international relations since the 1640s were no longer fit for purpose. George III created the Foreign Office to coordinate international diplomacy and the Home Office to run domestic policy and the British colonies. Fox saw other advantages than administrative necessity. He believed that George had too much power and hoped that the new Secretaries of State could force the king to accept American independence. "