While BoJo was speculated to be unhappy with May's deal, many suggested that he was willing to fall in line; however events over the past 24 hours changed his mind.
Theresa May promptly accepted Johnson's resignation with the following brief statement:
"This afternoon, the Prime Minister accepted the resignation of Boris Johnson as Foreign Secretary. His replacement will be announced shortly. The Prime Minister thanks Boris for his work'"
Johnson's resignation increases the chances that May will now face a leadership challenge over her Brexit policy.