When the Times Crossword is first introduced to the prisoners, the clue for 1 Across is stated as "What did Jupiter drop?" However, when Farrow has completed it, we see the 1 Across clue as "Preserve of Fiction" (solution:"ramjam"). Furthermore, the crossword is numbered #4548 whilst the solution to the previous day's crossword = #9547 - the leading "9" having been amended to a "4".
The two escapers would have covered up the tunnel exit, so that if the Germans did not discover it in their search , it could be used again.