The former Commonwealth champion was handed a 2012 technical decision win over Olubamiwo after suffering a bad cut. It set up an inevitable return because of the way that fight had ended.
This time around, Sexton, 29, took every session of the bout to record a shut-out 60-54 win. However, confusion over a standing count for Olubamiwo may have seen that card come back as 60-53.
Sexton is one of the names mentioned to fight for the British title vacated by David Price. A decision is due from the British Board in the coming weeks.
Elsewhere at York Hall, ex-pro footballer Leon McKenzie remained unbeaten since deciding to extend his family tradition by entering the ring as he took out Nikola Varbanov in just two rounds.
The 35-year-old connected with some brutal body shots that the young Bulgarian couldn’t take and the fight was over early in the round. McKenzie pushed his record to 3-0-1 with his second career stoppage and kept driving towards his dream of a possible English title shot.
On top of the billing at the famous London venue, George Jupp improved to 9-2 by overcoming Gia Atenov at the super-featherweight limit, meaning the 23-year-old has now won his last six fights on the spin.
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