Dear Johns
I must say, I've never heard "Dear and Slow" used for P&O. It doesn't really make sense. In that P&O carried the mails, their boats ran to a schedule determined by the GPO, and they got penalised if they didn't keep to it. I dare say it was dear, when you were hoarding every rupee to spend when you got home, but I doubt if it was exorbitant - I don't think P&O had a monopoly to India, though undoubtedly they predominated in the trade.
But if Kipling had invented a nickname for P&O, I think he'd have invented something cleverer. I mean, in the Victorian era, many of the railways in the UK had nicknames which were a play on their initials, and characteristics - e.g., the GWR (Great Western Railway) was known as the Great Way Round (because, until 1906, its main line to Cornwall went round via Bristol). The London, Chatham and Dover Railway was known as the London, Smashem and Turnover (rather unfairly, because its safety record was pretty good). The Somerset and Dorset was known as the Slow and Dirty (both of which it was). And the Manchester, Sheffield and Lincoln, an impecunious concern which was always behind with its dividends was known as the Money Sunk and Lost. Later on, it had delusions of grandeur, built a superb main line to London in 1899, renamed itself the Great Central Railway - which was promptly (and truly) said to stand for Gone Completely.
All those are apposite, and even, by Victorian standards, witty. I feel sure that KIpling would have done better with P&O.
Not terribly helpful, I fear.
Yours,
Alastair