It is a bit of a bizarre situation.
Say you went to Stratford races and stood in the Tats, watching the prices, when you heard one of the hands say "Tikay Max's owner has told a close friend they've trained him for this race, not the Gold Cup in a couple of weeks. Get the price down!" The bookies start to wipe 8/1 off and chalk up 4/1 but the one right at the bottom end hasn't heard yet. You run down and get your score on at the 8/1 he's offering.
You've done nothing wrong and the bookie can't say after he's handed you the slip and it's romped home "sorry son. Didn't realise it should have been half the price. Here's £100"
Online, he can. It's bizarre.
No emails or phone calls so probs being freerolled.