Irregular Webcomic! #3750

I thought to myself: What very British thing can happen to have delayed Sallah's arrival?

The answer came to me about 30 milliseconds later.

EDIT: Originally, the fourth panel read as follows:

4 Caption: In Southampton:
4 Rail employee: Great Western Railway apologises for the inconvenience. Honestly, if you want to get to Tintagel, you're better off walking.

However I received the following email from Transport Historian Dr Rudi Newman:

Seeing today's webcomic made me wonder about the accuracy of the final panel, and led to an interesting little historical exercise I'd like to share. Some while back you might recall a lengthy debate on Britain's railway network, of which I was a contributor (it correlating with my Ph.D.). This time it may be slightly [very] pedantic, but your annotations show that there's always space for accuracy.
The last panel notes "In Southampton" and "Great Western Railway" (that being the modern name, technically it was "The" Great Western Railway, but I digress). The primary rail link from Southampton up to the 1921 Grouping Act, whereby over a hundred railway companies were amalgamated into the "Big Four", was the London and South Western Railway (LSWR), which was sufficiently important that it owned/developed much of Southampton Docks. After the Grouping it became part of the Southern Railway (SR) until nationalisation in 1948. By comparison, the Great Western Railway (GWR) retained its corporate identity throughout until nationalisation (arguably even afterwards and now recently re-adopted). To travel efficiently to Tintagel would thus require travelling from Southampton to Waterloo, transferring to Paddington, and only then taking the GWR (then in Cornwall transferring again, ultimately disembarking at Camelford on the ex-North Cornwall Railway taken over by the LSWR). One could have taken the entire route via the LSWR/SR, but this potentially involved more changes, the GWR Penzance main line being more direct. This therefore suggests that for the initial Southampton stretch you referenced the wrong company in the panel.
However...
A lesser-known railway was constructed in sections c.1873-1885 called the Didcot, Newbury and Southampton Railway (DNSR), running between Southampton and the GWR main line at Didcot. Independently owned until the 1921 Grouping, it was taken over by the GWR (who had previously run it) so extending their operations in competition with the LSWR. In the 1950s, after nationalisation, it was ultimately put under the ex-SR Southern Division. To travel to Tintagel via this route would thus require travelling from Southampton to Didcot, there transferring directly onto the GWR main line - cutting out London entirely and shortening the mileage. Consequently this suggests that (pre-1948) you referenced the right company in the panel.
However...
The DNSR was far from either an important or successful railway. While ironically becoming vital for moving supplies in the build-up to D-Day, the line was sufficiently minor that its rolling stock ultimately included celebrity record-breaker 3440 City of Truro (the first engine to do 100 mph - which coincidently I've fired) as essentially a retirement job after being deemed obsolete and surplus to requirements, but nonetheless preserved. Speed and up-to-date rolling stock was plainly not of importance here! Consequently services on the line were slow and unreliable, and becoming all but a freight-only route, passenger trains became increasingly few and far between, particularly by the 1950s. One could argue the exact timing of the Cliffhangers thread, but immaterial of this passenger services were probably still poor.
As a result, while the Southampton-Didcot route was shorter in terms of mileage, waiting for connections, a limited number of services, and overall slower travelling means that the quicker and more comfortable route would have been the former via Waterloo and the LSWR. The GWR would, no doubt, have apologised for the inconvenience of the irregular service - as your station attendant does - but with rampant competition between companies may well have not recommended a competitor's service (LSWR/SR), so also covering your quip about walking.
Therefore your final panel is entirely accurate, albeit not as clear-cut as it may originally have seemed.
I can just imagine a final panel, though, with Sallah muttering about going by LSWR/SR instead. A pity it would not be particularly funny.
However... (I'm sure you see a trend here)
As the longer route would ultimately have been quicker than the shorter route, Sallah could have noted he seemed to be going a great (i.e. long) way round. Most railway companies had both positive and derogatory nicknames, the GWR being "God's Wonderful Railway" to its fans, but the long and winding route chosen by Brunel (as it had fewer gradients) was labelled by its detractors as the "Great Way Round" - a pun apposite for Sallah's situation, which any true-blood railway historian would find hilarious.
... good thing explaining a joke doesn't remove the humour!

Well, this correspondence was so long, so erudite, and so pedantically nerdy, that I felt compelled to adopt its advice into making the original comic even more erudite, nerdy, and - for true-blood railway historians - much more hilarious.

You can enjoy the revamped and much funnier comic above.