Grease a shallow 7 in square cake tin. Melt the butter with the sugar and syrup and pour on to the rolled oats. Mix well, turn the mixture into the prepared tin and press down well. Bake in the oven at 350F for about 20 minutes, until golden brown. Cool slightly in the tin, mark into fingers with a sharp knife and loosen round the edges. When firm, remove from the tin, and cool on a wire rack, then break into fingers. The flapjacks may be stored in an airtight container for up to a week.