Eva sets an impossible puzzle

Here's a description of the contestant's attempt. Someone's probably working on collecting some images to illustrate it.

Eva bases two of her clues on things that are not reliably replicable, such as the time it takes Mark to suck a lollipop down to the stick, and the time it takes to melt a cheese stick. The third clue is at least based on something tangible: the number of grapes she has placed on a dexterity toy. However, she completely forgets to set a clue for the fourth digit of her code, and it also later transpires that she wrote down an incorrect calculation step for one of the other digits anyway. She sets the code for the safe as '4447' before Mark asks whether he thinks someone would be able to solve it in under 20 minutes. At this point, it becomes apparent that she had also forgotten about the time constraint on the puzzle. Amazingly, Martin almost solves the puzzle in time, through sheer luck, but cracks the fourth digit of the code just after the time has run out, at 20 minutes and 5 seconds. Eva therefore receives no points for this task.

(Written by Karl Craven)