Veteran Finnish striker, Mixu Paatelainen, was both hero and villain as Saints maintained their unbeaten record, scoring the only goal and then earning a red card as his teammates battled heriocally to stave off wave after wave of Accies attacks.
Saints, knowing that a win would send them to the top of the table if Clyde lost, went quickly on the attack. John O'Neill had a drive saved by David McEwan and Hugh Murray fired in a tremendous effort from 20 yards which whistled inches wide with the keeper beaten.
Accies offered little by way of response, Craig Hinchcliffe dealing capably with long- range shots from Ryan Blackadder and Brian Carrigan. It was all St Mirren and they deserved to open the scoring.
Carrigan was caught in possession ten yards inside his own half by Mark Reilly and watched in horror as Reilly released Paatelainen, who strolled forward to smash a low angled drive beyond McEwan from 14 yards.
Hamilton roared back on the restart. Hinchcliffe made a fabulous save from Richard Waddell after a clever build-up from David Hamilton and Brian McPhee, and a Mark Corcoran lob was going in only for Kirk Broadfoot to clear acrobatically for a corner.
Saints were wilting under a constant barrage and Accies forced nine corners, but inspired by courageous last-ditch tackles by Broadfoot and David van Zanten, the home side somehow kept a clean sheet, despite Paatelainen being sent off for foolish persistent infringements.