A serious oil spill and heavy rain have caused the abandonment of the Sunflower Trophy races at Bishopscourt.
Race officials worked tirelessly to clear the County Down track before the decision to call off the meeting was taken midway through the afternoon.
Before proceedings were brought to a halt, Alastair Seeley was a convincing winner of the Supersport 600 race, with England's Luke Hedger in second.
Marshall Neill had set the pole position time for the feature event.
Wilson Craig Honda rider Neill qualified ahead of fellow Northern Ireland riders David Haire and Nico Mawhinney, with Scot Stuart Easton fourth fastest and Seeley fifth.
The cancellation of the 'big bike' races at the Sunflower meeting left Mawhinney as the new Irish Superbike champion, as he led the series going into the final series of races at Bishopscourt.
The meeting is regarded as Ireland's premier short circuit event, but did not take place last year as a change of date to mid-summer failed to attract a sufficient quality of entry from the top teams and riders.