I think it might be more along the lines of, you sponsor someone for a fiver on the spur of the moment and then you forget about it, and a couple of weeks later they come round with the envelope and you're totally happy to give it to them, you're not going back on your promise, BUT you don't have your wallet handy, or it's your last fiver until you get to a cashpoint and you need it to buy lunch today, but you'll definitely give it to them tomorrow, and then tomorrow comes and oops, forgot again, mind like a sieve... Just a question of scaling up from £5 to £5,000. Or maybe the cheques are in the post.