Coke's Secret Plan

The officers – and Coke – are enjoying tasty local chicken, beautifully-cooked French fries and a nice Burgundy wine. Except for the driver – who is drinking lemonade.‘This is my only chance – I have to do this!’ – thinks Coke. He asks to be excused. The officers nod wearily. Being a policeman is a hard job.
There is no chance that Coke will escape from the pub, because there is moorland all around – and he could easily be seen and recaptured. Moreover, he might need that help from the police when he comes out of prison. Coke looks carefully at the drystone walls in the yard. One side is 70 stones high and 178 stones long. The other wall – the west wall – is 71 stones high and 163 stones long. He can see the sun setting in the west. He takes his credit card and pushes it well into the gap between the stones at a point 39 stones up and 33 – his age – from the end of the north-west wall. Then he returns to the pub.