It's hard to imagine now how popular tandems used to be. There's still tons of venerable models floating around, they are largely unloved - just have a look on ebay and see how many there are. Nowadays they don't command very much money as few want to ride them and they take up a lot of space but back in the day they were very much a thing.
I can remember stories from my grandparents about their tandem adventures. One set of grandparents bought a tandem in the thirties and went on day trips from their home in Mansfield over to Skegness. Another set used to own a gorgeous flat tank Norton Model 18 combination which was traded in sometime in the mid to late thirties for a tandem. Doesn't seem like a fair exchange now!
Anyway here is a photo from the forgotten era of tandems. The bike is fully loaded up, even with a map holder on the handlebars, and it looks rather like the couple are on holiday in the Lake District. Happy times no doubt!