Keeping it brief:
Trying to catch a flight 45 years ago (as a teen), we were delayed by an ice storm enroute to the airport. Dashed to the ticketing booth literally at the departure time, told them "We're here and on our way" and ran to the gate (no security stops at all at that time - about 4 minutes). They (Continental) held the flight for us.
A week later, my dad received a polite letter simply pointing out that holding a flight could cost as much as $10000/£3500 (1970 currencies) and requesting that we plan better in future. No bill.
Times have changed, and while I am/was deeply grateful for what the airline did back then, now that I have first-hand knowledge of airline costs, I figure this person got off lightly at £6800 in 2016.