Waaaay back in about 2004 I was at the end of a two day Polaris mountain bike trailquest in the North York moors, I was knackered and I had about three road miles left back to the finish line and not quite enough time. A gent on a shiny road bike caught up with me and we got chatting; as soon as he realised I was in danger of being hit with a time penalty he offered me a wheel and towed me back and I made it with about two minutes to spare.
To my eternal shame I was so overwhelmed at finishing after a gruelling two day event that I just peeled off into the event centre and didn't thank him, I remember seeing him glance over his shoulder at me. So if he's reading this: "Sorry for my bad manners!"