Tom and Alex were two men working at a construction site. One day, Alex made a challenge to his stronger and faster counterpart: "I'll make you a bet: one after the other, we run with the wheelbarrow to the end of the building and back. Whoever's quickest wins. But there has to be one thing in the wheelbarrow all the time, and I choose what it is. I bet you £50" (for the Americans on the site, that's about $100).
"You're on," replied Tom.
Alex then chose what to put in the wheelbarrow. They had the race, and Alex won. Tom handed over the £50 in disgust.
What did Alex put in the wheelbarrow?