Misc photo seeking info on who, when & where?

Writing on the back of the photo says, ‘Medallists (back row, left to right) Peter Smith (bar to Gold)  David Preston (Gold), Graham McKnight (guest of honour), Alan Blue (Silver), Colin Greenhalgh (Perkin), David Beaumont (Bronze), John Dawson (Centenary). Front row – Geoffrey Pearson (Gold), Derek Byrne (President), Leslie Miles (Bar to Silver)’.