For the final preliminary 'free-roam' trial, the nine shortlisted rats were placed in a 9x9 space, and their movements were observed and recorded. Each of the digits 1-9 appeared in each row and column. OBSERVATIONS: Every cell in the grid was visited, exactly once; No rat's path contained any repeated digits; No rat chose to move diagonally at any point; Every 2x2 area was visited by at least 2 rats; No two rats started on the same digit; No two rats ended on the same digit; All blackcurrants and redcurrants were eaten; and No grapes were eaten. If a blackcurrant sits between two digits, one is double the other. If a redcurrant sits between two digits, one is odd and the other is even. If a grape sits between two digits, they have a difference of at least 5.