How on earth is it possible for a person to end up in jail for failure to attend unless the prosecution can demonstrate that the letter was delivered, by sending it recorded delivery for instance? There are so many other aspects of law where service has to be demonstrated - even the Small Claims Court requires proof of posting, as do eviction proceedings.
This is yet another layer of fear added to everything else that people in this situation worry about. I'm watching the post feverishly enough as it is. :-(
'Mongolian Warriors had the courage of lions, the patience of hounds, the prudence of cranes, the long-sightedness of ravens, the wildness of wolves, the passion of fightingcocks, the keenness of cats, the fury of wild boars and the cunning of foxes.' BE A MONGOLIAN WARRIOR WHEN DEFENDING YOUR INNOCENCE!