The two Londoners put their friendship aside to put on a thrilling fight in the capital, one which also had the carrot of becoming mandatory for the WBA belt.
Most experts predicted a back-and-forth fight and that is how it played out, albeit with Buatsi having the better success and achieving two knockdowns in the 11th round.
After the pair shared an embrace at the final bell, the judges scorecards read 116-110, 117-109 and 117-109 respectively, fair assessments of an entertaining tussle.
Although the bout took a bit of time to catch fire, it soon captivated an 8,000-strong crowd at Wembley Arena, even with Buatsi building a lead over an opponent who was gradually outclassed.
Even though there were numerous punishing exchanges, Buatsi was benefitting from landing the harder blows, seemingly gradually draining the tank of Azeez who would have realised that he was behind.
Azeez responded by edging at least one of the latter rounds to close the gap, but Buatsi twice floored Azeez - with the aid of a wet canvas - in the 11th to establish an unassailable lead.
With a minute to go, having again come out inferior as they ferociously traded for the umpteenth time, Azeez looked spent, and it enabled Buatsi to relatively cruise through the closing seconds to seal the standout victory of his career thus far.