Three minutes into injury time the match appeared to be over as Everitt put London Irish back in front at 22-21 with a drop goal but, in an extended spell of added time, Barkley had the final say.
Michalak merely took up the baton from Skrela though, booting two penalties and a drop-goal during a 15-minute spell that saw Toulouse effortlessly move 16-0 ahead.