The grandfather watches for a few minutes and then says "If you can get it to go in the hole, I'll give you £5"
The boy has a few more unsuccessful attempts and then gets up, goes into the kitchen and returns with a tin of spray starch. He sprays the worm and then puts it straight down the hole and turns triumphantly to his granddad.
The Grandfather says "well done" and hands over the money, takes the starch and goes into the house. He returns 15 minutes later, bends down to the boy and says
Spoiler:

