Edmund Burke
At this point, Fox whispered that there was "no loss of friendship". "I regret to say there is", Burke replied, "I have indeed made a great sacrifice; I have done my duty though I have lost my friend. There is something in the detested French constitution that envenoms every thing it touches". This provoked a reply from Fox, yet he was unable to give his speech for some time since he was overcome with tears and emotion, he appealed to Burke to remember their inalienable friendship, but also repeated his criticisms of Burke and uttered "unusually bitter sarcasms". This only aggravated the rupture between the two men. Burke demonstrated his separation from the party on 5 June 1791 by writing to Fitzwilliam, declining money from him.

Q: Who thought that Fox and Burke's friendship was lost?
Burke