Manor Park to Stonebridge Park via Kings Cross, Leeds, Settle, Carlisle and Euston! First Class Anytime Day Single... Thanks to the infamous Webtis error a few years ago!
The "WebTis specials" were some great trips. I had a great journey on a WebTis special on that route too with other forum members; whilst others went up the East Coast, myself and one other member decided on a slightly different route to get to Leeds involving East Midlands to Sheffield and changing there. Due to a delay at Trent Junction, we missed our originally planned connection (and the back up connection) at Sheffield. There was a Northern service that going by the timetable would mean we missed the Settle & Carlisle train with everyone else at Leeds, but looking at the journey history almost always seemed to arrive significantly early.
We approached the guard on the Northern service to explain why we were late and to ask if there was a slight possibility that the connection could be held, and were a bit nervous about the reaction owing to the ticket's destination, but much to our amazement he replied with "Ah, Stonebridge Park, that's in Glasgow isn't it?"
Lucky for us, the service did indeed arrive early and we ended up with a few minutes to spare onto the S&C train. The guard off our train from Sheffield even popped over to the S&C train to check we'd got there, he tapped on the window and waved us off!
Not sure if the Kent Flyer, WebTis specials or the as-yet-unnamed Scottish £1 tickets count as true loopholes or not, but my favourite loopholes involving Routeing Guide anomalies must have saved me hundreds of pounds over several years for journeys to see family. Primarily, these were London to Oxford via Newport (South Wales), and Hereford to Bristol via Birmingham. With regard to the latter, as soon as this was withdrawn by way of a negative easement I set out to find an alternative ticket and after a short browse of local area maps and the Routeing Guide I found an even cheaper ticket. Had they not have changed the guide then I'd have paid them more